1
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Ayub H, Murray RJ, Kuyler GC, Napier-Khwaja F, Gunner J, Dafforn TR, Klumperman B, Poyner DR, Wheatley M. GPCRs in the round: SMA-like copolymers and SMALPs as a platform for investigating GPCRs. Arch Biochem Biophys 2024; 754:109946. [PMID: 38395122 DOI: 10.1016/j.abb.2024.109946] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2023] [Revised: 01/21/2024] [Accepted: 02/20/2024] [Indexed: 02/25/2024]
Abstract
G-protein-coupled receptors (GPCRs) are the largest family of membrane proteins, regulate a plethora of physiological responses and are the therapeutic target for 30-40% of clinically-prescribed drugs. They are integral membrane proteins deeply embedded in the plasma membrane where they activate intracellular signalling via coupling to G-proteins and β-arrestin. GPCRs are in intimate association with the bilayer lipids and that lipid environment regulates the signalling functions of GPCRs. This complex lipid 'landscape' is both heterogeneous and dynamic. GPCR function is modulated by bulk membrane properties including membrane fluidity, microdomains, curvature, thickness and asymmetry but GPCRs are also regulated by specific lipid:GPCR binding, including cholesterol and anionic lipids. Understanding the molecular mechanisms whereby GPCR signalling is regulated by lipids is a very active area of research currently. A major advance in membrane protein research in recent years was the application of poly(styrene-co-maleic acid) (SMA) copolymers. These spontaneously generate SMA lipid particles (SMALPs) encapsulating membrane protein in a nano-scale disc of cell membrane, thereby removing the historical need for detergent and preserving lipid:GPCR interaction. The focus of this review is how GPCR-SMALPs are increasing our understanding of GPCR structure and function at the molecular level. Furthermore, an increasing number of 'second generation' SMA-like copolymers have been reported recently. These are reviewed from the context of increasing our understanding of GPCR molecular mechanisms. Moreover, their potential as a novel platform for downstream biophysical and structural analyses is assessed and looking ahead, the translational application of SMA-like copolymers to GPCR drug discovery programmes in the future is considered.
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Affiliation(s)
- Hoor Ayub
- Centre for Health and Life Sciences, Coventry University, Coventry, CV1 2DS, UK.
| | - Rebecca J Murray
- Centre for Health and Life Sciences, Coventry University, Coventry, CV1 2DS, UK; Department of Chemistry and Polymer Sciences, Stellenbosch University, Private Bag X1, Matieland, 7602, South Africa
| | - Gestél C Kuyler
- Centre for Health and Life Sciences, Coventry University, Coventry, CV1 2DS, UK; Department of Chemistry and Polymer Sciences, Stellenbosch University, Private Bag X1, Matieland, 7602, South Africa
| | | | - Joseph Gunner
- School of Life and Health Sciences, Aston University, Birmingham, B4 7ET, UK
| | - Tim R Dafforn
- School of Biosciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
| | - Bert Klumperman
- Department of Chemistry and Polymer Sciences, Stellenbosch University, Private Bag X1, Matieland, 7602, South Africa
| | - David R Poyner
- School of Life and Health Sciences, Aston University, Birmingham, B4 7ET, UK
| | - Mark Wheatley
- Centre for Health and Life Sciences, Coventry University, Coventry, CV1 2DS, UK; Centre of Membrane Proteins and Receptors (COMPARE), University of Birmingham and University of Nottingham, Midlands, UK
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2
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Ullrich J, Haueis L, Ohlhoff C, Zemella A, Kubick S, Stech M. Solubilization of Oligomeric Cell-Free Synthesized Proteins Using SMA Copolymers. Methods Mol Biol 2024; 2762:293-308. [PMID: 38315373 DOI: 10.1007/978-1-0716-3666-4_18] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2024]
Abstract
Although membrane proteins are abundant in nature, their investigation is limited due to bottlenecks in heterologous overexpression and consequently restricted accessibility for downstream applications. In this chapter, we address these challenges by presenting a fast and straightforward synthesis platform based on eukaryotic cell-free protein synthesis (CFPS) and an efficient solubilization strategy using styrene-maleic acid (SMA) copolymers. We demonstrate CFPS of TWIK-1, a dimeric ion channel, based on Sf21 (Spodoptera frugiperda) insect lysate showing homooligomerization and N-glycosylation enabled by endoplasmic reticulum-derived microsomes. Furthermore, we employ SMA copolymers for protein solubilization, which preserves the native-like microsomal environment. This approach not only retains the solubilized protein's suitability for downstream applications but also maintains the oligomerization and glycosylation of TWIK-1 post-solubilization. We validate the solubilization procedure using autoradiography, particle size analysis, and biomolecular fluorescence assay and confirm the very efficient, structurally intact solubilization of cell-free synthesized TWIK-1.
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Affiliation(s)
- Jessica Ullrich
- Fraunhofer Institute for Cell Therapy and Immunology (IZI), Branch Bioanalytics and Bioprocesses (IZI-BB), Potsdam, Germany
- Institute of Biotechnology, Technische Universität Berlin, Berlin, Germany
| | - Lisa Haueis
- Fraunhofer Institute for Cell Therapy and Immunology (IZI), Branch Bioanalytics and Bioprocesses (IZI-BB), Potsdam, Germany
- Institute of Biochemistry and Biology, University of Potsdam, Potsdam, Germany
| | - Carsten Ohlhoff
- Fraunhofer Institute for Cell Therapy and Immunology (IZI), Branch Bioanalytics and Bioprocesses (IZI-BB), Potsdam, Germany
| | - Anne Zemella
- Fraunhofer Institute for Cell Therapy and Immunology (IZI), Branch Bioanalytics and Bioprocesses (IZI-BB), Potsdam, Germany
| | - Stefan Kubick
- Fraunhofer Institute for Cell Therapy and Immunology (IZI), Branch Bioanalytics and Bioprocesses (IZI-BB), Potsdam, Germany
- Institute of Chemistry and Biochemistry, Freie Universität Berlin, Berlin, Germany
- Faculty of Health Sciences, Joint Faculty of the Brandenburg University of Technology Cottbus-Senftenberg, The Brandenburg Medical School Theodor Fontane and the University of Potsdam, Potsdam, Germany
| | - Marlitt Stech
- Fraunhofer Institute for Cell Therapy and Immunology (IZI), Branch Bioanalytics and Bioprocesses (IZI-BB), Potsdam, Germany.
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3
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Thomas B, Chockalingam K, Chen Z. Methods for Engineering Binders to Multi-Pass Membrane Proteins. Bioengineering (Basel) 2023; 10:1351. [PMID: 38135942 PMCID: PMC10741020 DOI: 10.3390/bioengineering10121351] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2023] [Revised: 11/11/2023] [Accepted: 11/19/2023] [Indexed: 12/24/2023] Open
Abstract
Numerous potential drug targets, including G-protein-coupled receptors and ion channel proteins, reside on the cell surface as multi-pass membrane proteins. Unfortunately, despite advances in engineering technologies, engineering biologics against multi-pass membrane proteins remains a formidable task. In this review, we focus on the different methods used to prepare/present multi-pass transmembrane proteins for engineering target-specific biologics such as antibodies, nanobodies and synthetic scaffold proteins. The engineered biologics exhibit high specificity and affinity, and have broad applications as therapeutics, probes for cell staining and chaperones for promoting protein crystallization. We primarily cover publications on this topic from the past 10 years, with a focus on the different formats of multi-pass transmembrane proteins. Finally, the remaining challenges facing this field and new technologies developed to overcome a number of obstacles are discussed.
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Affiliation(s)
- Benjamin Thomas
- Interdisciplinary Graduate Program in Genetics and Genomics, Texas A&M University, College Station, TX 77845, USA;
| | - Karuppiah Chockalingam
- Department of Microbial Pathogenesis and Immunology, Texas A&M University Health Science Center, Bryan, TX 77807, USA;
| | - Zhilei Chen
- Interdisciplinary Graduate Program in Genetics and Genomics, Texas A&M University, College Station, TX 77845, USA;
- Department of Microbial Pathogenesis and Immunology, Texas A&M University Health Science Center, Bryan, TX 77807, USA;
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4
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Neville GM, Morrison KA, Shilliday ER, Doutch J, Dalgliesh R, Price GJ, Edler KJ. The effect of polymer end-group on the formation of styrene - maleic acid lipid particles (SMALPs). SOFT MATTER 2023; 19:8507-8518. [PMID: 37889133 DOI: 10.1039/d3sm01180a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/28/2023]
Abstract
A series of block copolymers comprising styrene and maleic acid (SMA) has been prepared using RAFT polymerisation. RAFT often results in a large hydrophobic alkylthiocarbonylthio end group and this work examines its effect on the solution behaviour of the copolymers. SMA variants with, and without, this end group were synthesised and their behaviour compared with a commercially-available random copolymer of similar molecular weight. Dynamic light scattering and surface tension measurements found the RAFT-copolymers preferentially self-assembled into higher-order aggregates in aqueous solution. Small angle neutron scattering using deuterated styrene varients add support to the accepted model that these agreggates comprise a solvent-protected styrenic core with an acid-rich shell. Replacing the hydrophobic RAFT end group with a more hydrophilic nitrile caused differences in the resulting surface activity, attributed to the ability of the adjoining styrene homoblock to drive aggregation. Each of the copolymers formed SMALP nanodiscs with DMPC lipids, which were found to encapsulate a model membrane protein, gramicidin. However, end group variation affected solubilisition of DPPC, a lipid with a higher phase transition temperature. When using RAFT-copolymers terminated with a hydrophobic group, swelling of the bilayer and greater penetration of the homoblock into the nanodisc core occurred with increasing homoblock length. Conversely, commercial and nitrile-terminated RAFT-copolymers produced nanodisc sizes that stayed constant, instead indicating interaction at the edge of the lipid patch. The results highlight how even minor changes to the copolymer can modify the amphiphilic balance between regions, knowledge useful towards optimising copolymer structure to enhance and control nanodisc formation.
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Affiliation(s)
- George M Neville
- Centre for Sustainable Chemical Technologies, University of Bath, Claverton Down, Bath, BA2 7AY, UK.
- Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, UK
| | - Kerrie A Morrison
- Centre for Sustainable Chemical Technologies, University of Bath, Claverton Down, Bath, BA2 7AY, UK.
- Department of Life Sciences, University of Bath, Claverton Down, Bath BA2 7AY, UK
| | - Ella R Shilliday
- Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, UK
| | - James Doutch
- ISIS Pulsed Neutron and Muon Source, Rutherford Appleton Laboratory, Didcot, OX11 0QX, UK
| | - Robert Dalgliesh
- ISIS Pulsed Neutron and Muon Source, Rutherford Appleton Laboratory, Didcot, OX11 0QX, UK
| | - Gareth J Price
- Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, UK
- Department of Chemistry, Khalifa University, P.O. Box 127788, Abu Dhabi, United Arab Emirates
| | - Karen J Edler
- Centre for Sustainable Chemical Technologies, University of Bath, Claverton Down, Bath, BA2 7AY, UK.
- Department of Life Sciences, University of Bath, Claverton Down, Bath BA2 7AY, UK
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5
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Janata M, Gupta S, Čadová E, Angelisová P, Krishnarjuna B, Ramamoorthy A, Hořejší V, Raus V. Sulfonated polystyrenes: pH and Mg 2+-insensitive amphiphilic copolymers for detergent-free membrane protein isolation. Eur Polym J 2023; 198:112412. [PMID: 37780808 PMCID: PMC10538444 DOI: 10.1016/j.eurpolymj.2023.112412] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/03/2023]
Abstract
Amphiphilic polymers are increasingly applied in the detergent-free isolation and functional studies of membrane proteins. However, the carboxylate group present in the structure of many popular variants, such as styrene-maleic acid (SMA) copolymers, brings limitations in terms of polymer sensitivity to precipitation at acidic pH or in the presence of divalent metal cations. Herein, we addressed this problem by replacing carboxylate with the more acidic sulfonate groups. To this end, we synthesized a library of amphiphilic poly[styrene-co-(sodium 4-styrene sulfonate)] copolymers (termed SSS), differing in their molecular weight and overall polarity. Using model cell membranes (Jurkat), we identified two copolymer compositions (SSS-L30 and SSS-L36) that solubilized membranes to an extent similar to SMA. Interestingly, the density gradient ultracentrifugation/SDS-PAGE/Western blotting analysis of cell lysates revealed a distribution of studied membrane proteins in the gradient fractions that was different than for SMA-solubilized membranes. Importantly, unlike SMA, the SSS copolymers remained soluble at low pH and in the presence of Mg2+ ions. Additionally, the solubilization of DMPC liposomes by the lead materials was studied by turbidimetry, DLS, SEC, and high-resolution NMR, revealing, for SSS-L36, the formation of stable particles (nanodiscs), facilitated by the direct hydrophobic interaction of the copolymer phenyls with lipid acyl chains.
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Affiliation(s)
- Miroslav Janata
- Institute of Macromolecular Chemistry, Czech Academy of Sciences, Heyrovského nám. 2, 162 06 Prague 6, Czech Republic
| | - Sachin Gupta
- Institute of Macromolecular Chemistry, Czech Academy of Sciences, Heyrovského nám. 2, 162 06 Prague 6, Czech Republic
| | - Eva Čadová
- Institute of Macromolecular Chemistry, Czech Academy of Sciences, Heyrovského nám. 2, 162 06 Prague 6, Czech Republic
| | - Pavla Angelisová
- Institute of Molecular Genetics of the Czech Academy of Sciences, Vídeňská 1083, 142 20 Prague 4, Czech Republic
| | - Bankala Krishnarjuna
- Biophysics Program, Department of Chemistry, Macromolecular Science and Engineering, Biomedical Engineering, Michigan Neuroscience Institute, The University of Michigan, Ann Arbor, MI 48109-1055, USA
| | - Ayyalusamy Ramamoorthy
- Biophysics Program, Department of Chemistry, Macromolecular Science and Engineering, Biomedical Engineering, Michigan Neuroscience Institute, The University of Michigan, Ann Arbor, MI 48109-1055, USA
| | - Václav Hořejší
- Institute of Molecular Genetics of the Czech Academy of Sciences, Vídeňská 1083, 142 20 Prague 4, Czech Republic
| | - Vladimír Raus
- Institute of Macromolecular Chemistry, Czech Academy of Sciences, Heyrovského nám. 2, 162 06 Prague 6, Czech Republic
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6
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Scheyer MW, Campbell C, William PL, Hussain M, Begum A, Fonseca SE, Asare IK, Dabney P, Dabney-Smith C, Lorigan GA, Sahu ID. Electron paramagnetic resonance spectroscopic characterization of the human KCNE3 protein in lipodisq nanoparticles for structural dynamics of membrane proteins. Biophys Chem 2023; 301:107080. [PMID: 37531799 DOI: 10.1016/j.bpc.2023.107080] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2023] [Revised: 07/07/2023] [Accepted: 07/24/2023] [Indexed: 08/04/2023]
Abstract
One of the major challenges in solubilization of membrane proteins is to find the optimal physiological environment for their biophysical studies. EPR spectroscopy is a powerful biophysical technique for studying the structural and dynamic properties of macromolecules. However, the challenges in the membrane protein sample preparation and flexible motion of the spin label limit the utilization of EPR spectroscopy to a majority of membrane protein systems in a physiological membrane-bound state. Recently, lipodisq nanoparticles or styrene-maleic acid copolymer-lipid nanoparticles (SMALPs) have emerged as a membrane mimetic system for investigating the structural studies of membrane proteins. However, its detail characterization for membrane protein studies is still poorly understood. Recently, we characterized the potassium channel membrane protein KCNQ1 voltage sensing domain (KCNQ1-VSD) and KCNE1 reconstituted into lipodisq nanoparticles using EPR spectroscopy. In this study, the potassium channel accessory protein KCNE3 containing flexible N- and C-termini was encapsulated into proteoliposomes and lipodisq nanoparticles and characterized for studying its structural and dynamic properties using nitroxide based site-directed spin labeling EPR spectroscopy. CW-EPR lineshape analysis data indicated an increase in spectral line broadenings with the addition of the styrene-maleic acid (SMA) polymer which approaches close to the rigid limit providing a homogeneous stabilization of the protein-lipid complex. Similarly, EPR DEER measurements indicated an enhanced quality of distance measurements with an increase in the phase memory time (Tm) values upon incorporation of the sample into lipodisq nanoparticles, when compared to proteoliposomes. These results agree with the solution NMR structural structure of the KCNE3 and EPR studies of other membrane proteins in lipodisq nanoparticles. This study along with our earlier studies will provide the reference characterization data that will provide benefit to the membrane protein researchers for studying structural dynamics of challenging membrane proteins.
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Affiliation(s)
- Matthew W Scheyer
- Natural Science Division, Campbellsville University, Campbellsville, KY 42718, USA
| | - Conner Campbell
- Natural Science Division, Campbellsville University, Campbellsville, KY 42718, USA
| | - Patrick L William
- Natural Science Division, Campbellsville University, Campbellsville, KY 42718, USA
| | - Mustakim Hussain
- Natural Science Division, Campbellsville University, Campbellsville, KY 42718, USA
| | - Afsana Begum
- Natural Science Division, Campbellsville University, Campbellsville, KY 42718, USA
| | | | - Isaac K Asare
- Natural Science Division, Campbellsville University, Campbellsville, KY 42718, USA
| | - Peyton Dabney
- Natural Science Division, Campbellsville University, Campbellsville, KY 42718, USA
| | - Carole Dabney-Smith
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056, USA
| | - Gary A Lorigan
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056, USA
| | - Indra D Sahu
- Natural Science Division, Campbellsville University, Campbellsville, KY 42718, USA; Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056, USA.
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7
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Rathnayake K, Patel U, Hunt EC, Singh N. Fabrication of a Dual-Targeted Liposome-Coated Mesoporous Silica Core-Shell Nanoassembly for Targeted Cancer Therapy. ACS OMEGA 2023; 8:34481-34498. [PMID: 37779923 PMCID: PMC10536893 DOI: 10.1021/acsomega.3c02901] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/27/2023] [Accepted: 09/04/2023] [Indexed: 10/03/2023]
Abstract
Nanoparticles have been suggested as drug-delivery systems for chemotherapeutic drugs to allow for controlled drug release profiles and selectivity to target cancer cells. In addition, nanoparticles can be used for the in situ generation and amplification of reactive oxygen species (ROS), which have been shown to be a promising strategy for cancer treatment. Thus, a targeted nanoscale drug-delivery platform could be used to synergistically improve cancer treatment by the action of chemotherapeutic drugs and ROS generation. Herein, we propose a promising chemotherapy strategy where the drug-loaded nanoparticles generate high doses of ROS together with the loaded ROS-generating chemotherapeutic drugs, which can damage the mitochondria and activate cell death, potentiating the therapeutic outcome in cancer therapy. In the present study, we have developed a dual-targeted drug-delivery nanoassembly consisting of a mesoporous silica core loaded with the chemotherapeutic, ROS-generating drug, paclitaxel (Px), and coated with a liposome layer for controlled drug release. Two different lung cancer-targeting ligands, folic acid and peptide GE11, were used to target the overexpressed nonsmall lung cancer receptors to create the final nanoassembly (MSN@Px) L-GF. Upon endocytosis by the cancer cells, the liposome layer was degraded by the intracellular lipases, and the drug was rapidly released at a rate of 65% within the first 20 h. In vitro studies confirmed that this nanoassembly was 8-fold more effective in cancer therapy compared to the free drug Px.
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Affiliation(s)
- Kavini Rathnayake
- Department of Chemistry, The
University of Alabama in Huntsville, Huntsville, Alabama 35899, United States
| | - Unnati Patel
- Department of Chemistry, The
University of Alabama in Huntsville, Huntsville, Alabama 35899, United States
| | - Emily C. Hunt
- Department of Chemistry, The
University of Alabama in Huntsville, Huntsville, Alabama 35899, United States
| | - Nirupama Singh
- Department of Chemistry, The
University of Alabama in Huntsville, Huntsville, Alabama 35899, United States
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8
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Trinh TKH, Cabezas AJ, Joshi S, Catalano C, Siddique AB, Qiu W, Deshmukh S, des Georges A, Guo Y. pH-tunable membrane-active polymers, NCMNP2a- x, and their potential membrane protein applications. Chem Sci 2023; 14:7310-7326. [PMID: 37416719 PMCID: PMC10321531 DOI: 10.1039/d3sc01890c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2023] [Accepted: 05/30/2023] [Indexed: 07/08/2023] Open
Abstract
Accurate 3D structures of membrane proteins are essential for comprehending their mechanisms of action and designing specific ligands to modulate their activities. However, these structures are still uncommon due to the involvement of detergents in the sample preparation. Recently, membrane-active polymers have emerged as an alternative to detergents, but their incompatibility with low pH and divalent cations has hindered their efficacy. Herein, we describe the design, synthesis, characterization, and application of a new class of pH-tunable membrane-active polymers, NCMNP2a-x. The results demonstrated that NCMNP2a-x could be used for high-resolution single-particle cryo-EM structural analysis of AcrB in various pH conditions and can effectively solubilize BcTSPO with the function preserved. Molecular dynamic simulation is consistent with experimental data that shed great insights into the working mechanism of this class of polymers. These results demonstrated that NCMNP2a-x might have broad applications in membrane protein research.
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Affiliation(s)
- Thi Kim Hoang Trinh
- Department of Medicinal Chemistry, School of Pharmacy, Virginia Commonwealth University Richmond VA 23298 USA
- Institute for Structural Biology, Drug Discovery and Development, School of Pharmacy, Virginia Commonwealth University Richmond VA 23219 USA
| | - Andres Jorge Cabezas
- Structural Biology Initiative, CUNY Advanced Science Research Center, City University of New York New York New York 10017 USA
- PhD Program in Biochemistry, The Graduate Center of the City University of New York New York New York 10017 USA
| | - Soumil Joshi
- Department of Chemical Engineering, Virginia Tech Blacksburg VA2 4060 USA
| | - Claudio Catalano
- Department of Medicinal Chemistry, School of Pharmacy, Virginia Commonwealth University Richmond VA 23298 USA
- Institute for Structural Biology, Drug Discovery and Development, School of Pharmacy, Virginia Commonwealth University Richmond VA 23219 USA
| | - Abu Bakkar Siddique
- Department of Medicinal Chemistry, School of Pharmacy, Virginia Commonwealth University Richmond VA 23298 USA
- Institute for Structural Biology, Drug Discovery and Development, School of Pharmacy, Virginia Commonwealth University Richmond VA 23219 USA
| | - Weihua Qiu
- Department of Medicinal Chemistry, School of Pharmacy, Virginia Commonwealth University Richmond VA 23298 USA
- Institute for Structural Biology, Drug Discovery and Development, School of Pharmacy, Virginia Commonwealth University Richmond VA 23219 USA
| | - Sanket Deshmukh
- Department of Chemical Engineering, Virginia Tech Blacksburg VA2 4060 USA
| | - Amedee des Georges
- Structural Biology Initiative, CUNY Advanced Science Research Center, City University of New York New York New York 10017 USA
- PhD Program in Biochemistry, The Graduate Center of the City University of New York New York New York 10017 USA
- Department of Chemistry & Biochemistry, City College of New York New York New York 10017 USA
| | - Youzhong Guo
- Department of Medicinal Chemistry, School of Pharmacy, Virginia Commonwealth University Richmond VA 23298 USA
- Institute for Structural Biology, Drug Discovery and Development, School of Pharmacy, Virginia Commonwealth University Richmond VA 23219 USA
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9
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Olivas TJ, Wu Y, Yu S, Luan L, Choi P, Guinn ED, Nag S, De Camilli PV, Gupta K, Melia TJ. ATG9 vesicles comprise the seed membrane of mammalian autophagosomes. J Cell Biol 2023; 222:e202208088. [PMID: 37115958 PMCID: PMC10148236 DOI: 10.1083/jcb.202208088] [Citation(s) in RCA: 17] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2022] [Revised: 03/20/2023] [Accepted: 04/05/2023] [Indexed: 04/30/2023] Open
Abstract
As the autophagosome forms, its membrane surface area expands rapidly, while its volume is kept low. Protein-mediated transfer of lipids from another organelle to the autophagosome likely drives this expansion, but as these lipids are only introduced into the cytoplasmic-facing leaflet of the organelle, full membrane growth also requires lipid scramblase activity. ATG9 harbors scramblase activity and is essential to autophagosome formation; however, whether ATG9 is integrated into mammalian autophagosomes remains unclear. Here we show that in the absence of lipid transport, ATG9 vesicles are already competent to collect proteins found on mature autophagosomes, including LC3-II. Further, we use styrene-maleic acid lipid particles to reveal the nanoscale organization of protein on LC3-II membranes; ATG9 and LC3-II are each fully integrated into expanding autophagosomes. The ratios of these two proteins at different stages of maturation demonstrate that ATG9 proteins are not continuously integrated, but rather are present on the seed vesicles only and become diluted in the expanding autophagosome membrane.
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Affiliation(s)
- Taryn J. Olivas
- Department of Cell Biology, School of Medicine, Yale University, New Haven, CT, USA
| | - Yumei Wu
- Department of Cell Biology, School of Medicine, Yale University, New Haven, CT, USA
- Department of Neuroscience, School of Medicine, Yale University, New Haven, CT, USA
- Howard Hughes Medical Institute, School of Medicine, Yale University, New Haven, CT, USA
- Program in Cellular Neuroscience Neurodegeneration and Repair, School of Medicine, Yale University, New Haven, CT, USA
| | - Shenliang Yu
- Department of Cell Biology, School of Medicine, Yale University, New Haven, CT, USA
| | - Lin Luan
- Department of Cell Biology, School of Medicine, Yale University, New Haven, CT, USA
| | - Peter Choi
- Department of Cell Biology, School of Medicine, Yale University, New Haven, CT, USA
| | - Emily D. Guinn
- Department of Cell Biology, School of Medicine, Yale University, New Haven, CT, USA
| | - Shanta Nag
- Department of Cell Biology, School of Medicine, Yale University, New Haven, CT, USA
| | - Pietro V. De Camilli
- Department of Cell Biology, School of Medicine, Yale University, New Haven, CT, USA
- Department of Neuroscience, School of Medicine, Yale University, New Haven, CT, USA
- Howard Hughes Medical Institute, School of Medicine, Yale University, New Haven, CT, USA
- Program in Cellular Neuroscience Neurodegeneration and Repair, School of Medicine, Yale University, New Haven, CT, USA
| | - Kallol Gupta
- Department of Cell Biology, School of Medicine, Yale University, New Haven, CT, USA
- Nanobiology Institute, Yale University, West Haven, CT, USA
| | - Thomas J. Melia
- Department of Cell Biology, School of Medicine, Yale University, New Haven, CT, USA
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10
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Zhou R, Zhang S, Nguyen HT, Ding H, Gaffney A, Kappes JC, Smith AB, Sodroski JG. Conformations of Human Immunodeficiency Virus Envelope Glycoproteins in Detergents and Styrene-Maleic Acid Lipid Particles. J Virol 2023; 97:e0032723. [PMID: 37255444 PMCID: PMC10308955 DOI: 10.1128/jvi.00327-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Accepted: 05/10/2023] [Indexed: 06/01/2023] Open
Abstract
The mature human immunodeficiency virus (HIV) envelope glycoprotein (Env) trimer, which consists of noncovalently associated gp120 exterior and gp41 transmembrane subunits, mediates virus entry into cells. The pretriggered (State-1) Env conformation is the major target for broadly neutralizing antibodies (bNAbs), whereas receptor-induced downstream Env conformations elicit immunodominant, poorly neutralizing antibody (pNAb) responses. To examine the contribution of membrane anchorage to the maintenance of the metastable pretriggered Env conformation, we compared wild-type and State-1-stabilized Envs solubilized in detergents or in styrene-maleic acid (SMA) copolymers. SMA directly incorporates membrane lipids and resident membrane proteins into lipid nanoparticles (styrene-maleic acid lipid particles [SMALPs]). The integrity of the Env trimer in SMALPs was maintained at both 4°C and room temperature. In contrast, Envs solubilized in Cymal-5, a nonionic detergent, were unstable at room temperature, although their stability was improved at 4°C and/or after incubation with the entry inhibitor BMS-806. Envs solubilized in ionic detergents were relatively unstable at either temperature. Comparison of Envs solubilized in Cymal-5 and SMA at 4°C revealed subtle differences in bNAb binding to the gp41 membrane-proximal external region, consistent with these distinct modes of Env solubilization. Otherwise, the antigenicity of the Cymal-5- and SMA-solubilized Envs was remarkably similar, both in the absence and in the presence of BMS-806. However, both solubilized Envs were recognized differently from the mature membrane Env by specific bNAbs and pNAbs. Thus, detergent-based and detergent-free solubilization at 4°C alters the pretriggered membrane Env conformation in consistent ways, suggesting that Env assumes default conformations when its association with the membrane is disrupted. IMPORTANCE The human immunodeficiency virus (HIV) envelope glycoproteins (Envs) in the viral membrane mediate virus entry into the host cell and are targeted by neutralizing antibodies elicited by natural infection or vaccines. Detailed studies of membrane proteins rely on purification procedures that allow the proteins to maintain their natural conformation. In this study, we show that a styrene-maleic acid (SMA) copolymer can extract HIV-1 Env from a membrane without the use of detergents. The Env in SMA is more stable at room temperature than Env in detergents. The purified Env in SMA maintains many but not all of the characteristics expected of the natural membrane Env. Our results underscore the importance of the membrane environment to the native conformation of HIV-1 Env. Purification methods that bypass the need for detergents could be useful tools for future studies of HIV-1 Env structure and its interaction with receptors and antibodies.
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Affiliation(s)
- Rong Zhou
- Department of Cancer Immunology and Virology, Dana-Farber Cancer Institute, Boston, Massachusetts, USA
- Department of Microbiology, Harvard Medical School, Boston, Massachusetts, USA
| | - Shijian Zhang
- Department of Cancer Immunology and Virology, Dana-Farber Cancer Institute, Boston, Massachusetts, USA
- Department of Microbiology, Harvard Medical School, Boston, Massachusetts, USA
| | - Hanh T. Nguyen
- Department of Cancer Immunology and Virology, Dana-Farber Cancer Institute, Boston, Massachusetts, USA
- Department of Microbiology, Harvard Medical School, Boston, Massachusetts, USA
| | - Haitao Ding
- Department of Medicine, University of Alabama at Birmingham, Alabama, USA
- Birmingham Veterans Affairs Medical Center, Research Service, Birmingham, Alabama, USA
| | - Althea Gaffney
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - John C. Kappes
- Department of Medicine, University of Alabama at Birmingham, Alabama, USA
- Birmingham Veterans Affairs Medical Center, Research Service, Birmingham, Alabama, USA
| | - Amos B. Smith
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Joseph G. Sodroski
- Department of Cancer Immunology and Virology, Dana-Farber Cancer Institute, Boston, Massachusetts, USA
- Department of Microbiology, Harvard Medical School, Boston, Massachusetts, USA
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11
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Kamilar E, Bariwal J, Zheng W, Ma H, Liang H. SMALPs Are Not Simply Nanodiscs: The Polymer-to-Lipid Ratios of Fractionated SMALPs Underline Their Heterogeneous Nature. Biomacromolecules 2023; 24:1819-1838. [PMID: 36947865 DOI: 10.1021/acs.biomac.3c00034] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/24/2023]
Abstract
Amphipathic styrene-maleic acid (SMA) copolymers directly solubilize biomembranes into SMA-lipid particles, or SMALPs, that are often regarded as nanodiscs and hailed as a native membrane platform. The promising outlook of SMALPs inspires the discovery of many SMA-like copolymers that also solubilize biomembranes into putative nanodiscs, but a fundamental question remains on how much the SMALPs or SMALP analogues truly resemble the bilayer structure of nanodiscs. This unfortunate ambiguity undermines the utility of SMA or SMA-like copolymers in membrane biology because the structure and function of many membrane proteins depend critically on their surrounding matrices. Here, we report the structural heterogeneity of SMALPs revealed through fractionating SMALPs comprised of lipids and well-defined SMAs via size-exclusion chromatography followed by quantitative determination of the polymer-to-lipid (P/L) stoichiometric ratios in individual fractions. Through the lens of P/L stoichiometric ratios, different self-assembled polymer-lipid nanostructures are inferred, such as polymer-remodeled liposomes, polymer-encased nanodiscs, polymer-lipid mixed micelles, and lipid-doped polymer micellar aggregates. We attribute the structural heterogeneity of SMALPs to the microstructure variations amongst individual polymer chains that give rise to their polydisperse detergency. As an example, we demonstrate that SMAs with a similar S/MA ratio but different chain sizes participate preferentially in different polymer-lipid nanostructures. We further demonstrate that proteorhodopsin, a light-driven proton pump solubilized within the same SMALPs is distributed amongst different self-assembled nanostructures to display different photocycle kinetics. Our discovery challenges the native nanodisc notion of SMALPs or SMALP analogues and highlights the necessity to separate and identify the structurally dissimilar polymer-lipid particles in membrane biology studies.
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Affiliation(s)
- Elizabeth Kamilar
- Department of Cell Physiology & Molecular Biophysics, Center for Membrane Protein Research, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, Texas 79430, United States
| | - Jitender Bariwal
- Department of Cell Physiology & Molecular Biophysics, Center for Membrane Protein Research, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, Texas 79430, United States
| | - Wan Zheng
- Department of Cell Physiology & Molecular Biophysics, Center for Membrane Protein Research, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, Texas 79430, United States
| | - Hairong Ma
- Department of Cell Physiology & Molecular Biophysics, Center for Membrane Protein Research, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, Texas 79430, United States
| | - Hongjun Liang
- Department of Cell Physiology & Molecular Biophysics, Center for Membrane Protein Research, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, Texas 79430, United States
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12
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Krishnarjuna B, Marte J, Ravula T, Ramamoorthy A. Enhancing the stability and homogeneity of non-ionic polymer nanodiscs by tuning electrostatic interactions. J Colloid Interface Sci 2023; 634:887-896. [PMID: 36566634 PMCID: PMC10838601 DOI: 10.1016/j.jcis.2022.12.112] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2022] [Revised: 12/14/2022] [Accepted: 12/19/2022] [Indexed: 12/24/2022]
Abstract
The nanodisc technology is increasingly used for structural studies on membrane proteins and drug delivery. The development of synthetic polymer nanodiscs and the recent discovery of non-ionic inulin-based polymers have significantly broadened the scope of nanodiscs. While the lipid exchange and size flexibility properties of the self-assembled polymer-based nanodiscs are valuable for various applications, the non-ionic polymer nanodiscs are remarkably unique in that they enable the reconstitution of any protein, protein-protein complexes, or drugs irrespective of their charge. However, the non-ionic nature of the belt could influence the stability and size homogeneity of inulin-based polymer nanodiscs. In this study, we investigate the size stability and homogeneity of nanodiscs formed by non-ionic lipid-solubilizing polymers using different biophysical methods. Polymer nanodiscs containing zwitterionic DMPC and different ratios of DMPC:DMPG lipids were made using anionic SMA-EA or non-ionic pentyl-inulin polymers. Non-ionic polymer nanodiscs made using zwitterionic DMPC lipids produced a very broad elution profile on SEC due to their instability in the column, thus affecting sample monodispersity which was confirmed by DLS experiments that showed multiple peaks. However, the inclusion of anionic DMPG lipids improved the stability as observed from SEC and DLS profiles, which was further confirmed by TEM images. Whereas, anionic SMA-EA-based DMPC-nanodiscs showed excellent stability and size homogeneity when solubilizing zwitterionic lipids. The stability of DMPC:DMPG non-ionic polymer nanodiscs is attributed to the inter-nanodisc repulsion by the anionic-DMPG that prevents the uncontrolled collision and fusion of nanodiscs. Thus, the reported results demonstrate the use of electrostatic interactions to tune the solubility, stability, and size homogeneity of non-ionic polymer nanodiscs which are important features for enabling functional and atomic-resolution structural studies of membrane proteins, other lipid-binding molecules, and water-soluble biomolecules including cytosolic proteins, nucleic acids and metabolites.
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Affiliation(s)
- Bankala Krishnarjuna
- Biophysics Program, Department of Chemistry, Macromolecular Science and Engineering, Biomedical Engineering, Michigan Neuroscience Institute, The University of Michigan, Ann Arbor, MI 48109-1055, USA
| | - Joseph Marte
- Biophysics Program, Department of Chemistry, Macromolecular Science and Engineering, Biomedical Engineering, Michigan Neuroscience Institute, The University of Michigan, Ann Arbor, MI 48109-1055, USA
| | - Thirupathi Ravula
- Biophysics Program, Department of Chemistry, Macromolecular Science and Engineering, Biomedical Engineering, Michigan Neuroscience Institute, The University of Michigan, Ann Arbor, MI 48109-1055, USA
| | - Ayyalusamy Ramamoorthy
- Biophysics Program, Department of Chemistry, Macromolecular Science and Engineering, Biomedical Engineering, Michigan Neuroscience Institute, The University of Michigan, Ann Arbor, MI 48109-1055, USA.
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13
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Harant K, Čajka T, Angelisová P, Pokorná J, Hořejší V. Composition of raft-like cell membrane microdomains resistant to styrene-maleic acid copolymer (SMA) solubilization. Biophys Chem 2023; 296:106989. [PMID: 36898346 DOI: 10.1016/j.bpc.2023.106989] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2022] [Revised: 02/21/2023] [Accepted: 02/28/2023] [Indexed: 03/08/2023]
Abstract
An advantageous alternative to the use of detergents in biochemical studies on membrane proteins are the recently developed styrene-maleic acid (SMA) amphipathic copolymers. In our recent study [1] we demonstrated that using this approach, most T cell membrane proteins were fully solubilized (presumably in small nanodiscs), while two types of raft proteins, GPI-anchored proteins and Src family kinases, were mostly present in much larger (>250 nm) membrane fragments markedly enriched in typical raft lipids, cholesterol and lipids containing saturated fatty acid residues. In the present study we demonstrate that disintegration of membranes of several other cell types by means of SMA copolymer follows a similar pattern and we provide a detailed proteomic and lipidomic characterization of these SMA-resistant membrane fragments (SRMs).
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Affiliation(s)
- Karel Harant
- Proteomics Core Facility, Faculty of Science, Charles University, BIOCEV, Prumyslova 595, Vestec CZ-25242, Czechia; Institute for Environmental Studies, Faculty of Science, Charles University, Benatska 2, Prague 2 CZ-128 01, Czechia.
| | - Tomáš Čajka
- Institute of Physiology of the Czech Academy of Sciences, Vídeňská, 1083 142 20 Praha 4, Czechia.
| | - Pavla Angelisová
- Institute of Molecular Genetics of the Czech Academy of Sciences, Vídeňská, 1083 142 20 Praha 4, Czechia
| | - Jana Pokorná
- Institute of Molecular Genetics of the Czech Academy of Sciences, Vídeňská, 1083 142 20 Praha 4, Czechia
| | - Václav Hořejší
- Institute of Molecular Genetics of the Czech Academy of Sciences, Vídeňská, 1083 142 20 Praha 4, Czechia.
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14
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Maier R, Cuevas Arenas R, Zhang F, García-Sáez A, Schreiber F. Structural Insights into Polymer-Bounded Lipid Nanodiscs. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:2450-2459. [PMID: 36724350 DOI: 10.1021/acs.langmuir.2c03412] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Membrane proteins are an essential part of signaling and transport processes and are targeted by multiple drugs. To isolate and investigate them in their native state, polymer-bounded nanodiscs have become valuable tools. In this study, we investigate the lipid model system dimyristoyl-phosphocholine (DMPC) with the nanodisc-forming copolymers styrene maleic acid (SMA) and diisobutylene maleic acid (DIBMA). Using small-angle X-ray scattering (SAXS) and dynamic light scattering (DLS), we studied the influence of polymer concentration and temperature on the nanodisc structure. In Tris buffer, the size of nanodiscs formed with SMA is smaller compared to DIBMA at the same polymer ratio. In both cases, the size decreases monotonically with increasing polymer concentration, and this effect is more pronounced when using SMA. Measurements at temperatures (T) between 5 and 30 °C in phosphate buffer showed an incomplete solubilization at high T even at polymer/lipid ratios above that required for complete lipid solubilization. For DIBMA, the nanodiscs developed at lower temperatures are stable and the net repulsion increases, while for SMA, the individual nanodiscs possess smaller sizes and are less affected by T. However, using DLS, one can observe SMA agglomerates at low T. Interestingly, for both polymers, no drastic changes of the observable parameters (radius and bilayer thickness) are seen upon cooling, which would indicate a sharp (first-order) phase transition from liquid-crystalline to gel, but only gradual changes. Hence, we conclude that the transition from a gel toward a liquid-crystalline lipid phase proceeds over a broad T-range compared to a continuous lipid bilayer. These results can pave the way toward the development of better protocols for studying membrane proteins stabilized in this type of membrane mimics.
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Affiliation(s)
- Ralph Maier
- Institut für Angewandte Physik, Universität Tübingen, Auf der Morgenstelle 10, 72076Tübingen, Germany
| | - Rodrigo Cuevas Arenas
- Interfakultäres Institut für Biochemie, Universität Tübingen, Hoppe-Seyler-Strasse 4, 72076Tübingen, Germany
- Bijvoet Center for Biomolecular Research, Utrecht University, Universiteitsweg 99, 3584CGUtrecht, Netherlands
| | - Fajun Zhang
- Institut für Angewandte Physik, Universität Tübingen, Auf der Morgenstelle 10, 72076Tübingen, Germany
| | - Ana García-Sáez
- Interfakultäres Institut für Biochemie, Universität Tübingen, Hoppe-Seyler-Strasse 4, 72076Tübingen, Germany
- Institut für Genetik, Universität zu Köln, Joseph-Stelzmann-Strasse 26, 50931Köln, Germany
| | - Frank Schreiber
- Institut für Angewandte Physik, Universität Tübingen, Auf der Morgenstelle 10, 72076Tübingen, Germany
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15
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Johansen NT, Tidemand FG, Pedersen MC, Arleth L. Travel light: Essential packing for membrane proteins with an active lifestyle. Biochimie 2023; 205:3-26. [PMID: 35963461 DOI: 10.1016/j.biochi.2022.07.014] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Revised: 06/29/2022] [Accepted: 07/23/2022] [Indexed: 11/02/2022]
Abstract
We review the considerable progress during the recent decade in the endeavours of designing, optimising, and utilising carrier particle systems for structural and functional studies of membrane proteins in near-native environments. New and improved systems are constantly emerging, novel studies push the perceived limits of a given carrier system, and specific carrier systems consolidate and entrench themselves as the system of choice for particular classes of target membrane protein systems. This review covers the most frequently used carrier systems for such studies and emphasises similarities and differences between these systems as well as current trends and future directions for the field. Particular interest is devoted to the biophysical properties and membrane mimicking ability of each system and the manner in which this may impact an embedded membrane protein and an eventual structural or functional study.
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Affiliation(s)
- Nicolai Tidemand Johansen
- Section for Transport Biology, Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, Frederiksberg C, 1871, Denmark.
| | - Frederik Grønbæk Tidemand
- Section for Transport Biology, Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, Frederiksberg C, 1871, Denmark
| | - Martin Cramer Pedersen
- Condensed Matter Physics, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, Copenhagen E, 2100, Denmark
| | - Lise Arleth
- Condensed Matter Physics, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, Copenhagen E, 2100, Denmark
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16
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Sinha S, Kumar S, Singh K, Umam F, Agrawal V, Aggarwal A, Imperiali B. Immunochemical characterisation of styrene maleic acid lipid particles prepared from Mycobacterium tuberculosis plasma membrane. PLoS One 2023; 18:e0280074. [PMID: 36608027 PMCID: PMC9821473 DOI: 10.1371/journal.pone.0280074] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2022] [Accepted: 12/20/2022] [Indexed: 01/07/2023] Open
Abstract
Membrane proteins of Mycobacterium tuberculosis (Mtb) can be targeted for the development of therapeutic and prophylactic interventions against tuberculosis. We have utilized the unique membrane-solubilising properties of the styrene maleic acid copolymer <styrene:maleic acid::2:1> (SMA) to prepare and characterise 'styrene maleic acid lipid particles' from the native membrane of Mtb (MtM-SMALPs). When resolved by SDS-PAGE and visualised with coomassie blue, the molecular weights of Mtb membrane (MtM) proteins solubilised by SMA were mostly in the range of 40-70 kDa. When visualised by transmission electron microscopy, MtM-SMALPs appeared as nanoparticles of discrete shapes and sizes. The discoid nanoparticles exhibited a range of diameters of ~10-90 nm, with largest portion (~61%) ranging from 20-40 nm. MtM proteins of a molecular weight-range overlapping with that of MtM-SMALPs were also amenable to chemical cross-linking, revealing protein complex formation. Characterisation using monoclonal antibodies against seven MtM-associated antigens confirmed the incorporation of the inner membrane protein PRA, membrane-associated proteins PstS1, LpqH and Ag85, and the lipoglycan LAM into MtM-SMALPs. Conversely, the peripheral membrane proteins Acr and PspA were nearly completely excluded. Furthermore, although MtM showed an abundance of Con A-binding glycoproteins, MtM-SMALPs appeared devoid of these species. Immune responses of healthcare workers harbouring 'latent TB infection' provided additional insights. While MtM-SMALPs and MtM induced comparable levels of the cytokine IFN-γ, only MtM-SMALPs could induce the production of TNF-α. Antibodies present in the donor sera showed significantly higher binding to MtM than to MtM-SMALPs. These results have implications for the development of MtM-based immunoprophylaxis against tuberculosis.
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Affiliation(s)
- Sudhir Sinha
- Department of Clinical Immunology & Rheumatology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, India
- * E-mail:
| | - Shashikant Kumar
- Department of Clinical Immunology & Rheumatology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, India
| | - Komal Singh
- Department of Clinical Immunology & Rheumatology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, India
| | - Fareha Umam
- Department of Clinical Immunology & Rheumatology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, India
| | - Vinita Agrawal
- Department of Pathology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, India
| | - Amita Aggarwal
- Department of Clinical Immunology & Rheumatology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, India
| | - Barbara Imperiali
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
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17
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Glueck D, Grethen A, Das M, Mmeka OP, Patallo EP, Meister A, Rajender R, Kins S, Räschle M, Victor J, Chu C, Etzkorn M, Köck Z, Bernhard F, Babalola JO, Vargas C, Keller S. Electroneutral Polymer Nanodiscs Enable Interference-Free Probing of Membrane Proteins in a Lipid-Bilayer Environment. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2022; 18:e2202492. [PMID: 36228092 DOI: 10.1002/smll.202202492] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2022] [Revised: 09/10/2022] [Indexed: 06/16/2023]
Abstract
Membrane proteins can be examined in near-native lipid-bilayer environments with the advent of polymer-encapsulated nanodiscs. These nanodiscs self-assemble directly from cellular membranes, allowing in vitro probing of membrane proteins with techniques that have previously been restricted to soluble or detergent-solubilized proteins. Often, however, the high charge densities of existing polymers obstruct bioanalytical and preparative techniques. Thus, the authors aim to fabricate electroneutral-yet water-soluble-polymer nanodiscs. By attaching a sulfobetaine group to the commercial polymers DIBMA and SMA(2:1), these polyanionic polymers are converted to the electroneutral maleimide derivatives, Sulfo-DIBMA and Sulfo-SMA(2:1). Sulfo-DIBMA and Sulfo-SMA(2:1) readily extract proteins and phospholipids from artificial and cellular membranes to form nanodiscs. Crucially, the electroneutral nanodiscs avert unspecific interactions, thereby enabling new insights into protein-lipid interactions through lab-on-a-chip detection and in vitro translation of membrane proteins. Finally, the authors create a library comprising thousands of human membrane proteins and use proteome profiling by mass spectrometry to show that protein complexes are preserved in electroneutral nanodiscs.
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Affiliation(s)
- David Glueck
- Molecular Biophysics, Technische Universität Kaiserslautern (TUK), Erwin-Schrödinger-Str. 13, 67663, Kaiserslautern, Germany
- Biophysics, Institute of Molecular Biosciences (IMB), NAWI Graz, University of Graz, Humboldtstr. 50/III, Graz, 8010, Austria
- Field of Excellence BioHealth, University of Graz, Graz, Austria
- BioTechMed-Graz, Graz, Austria
| | - Anne Grethen
- Molecular Biophysics, Technische Universität Kaiserslautern (TUK), Erwin-Schrödinger-Str. 13, 67663, Kaiserslautern, Germany
| | - Manabendra Das
- Molecular Biophysics, Technische Universität Kaiserslautern (TUK), Erwin-Schrödinger-Str. 13, 67663, Kaiserslautern, Germany
| | - Ogochukwu Patricia Mmeka
- Molecular Biophysics, Technische Universität Kaiserslautern (TUK), Erwin-Schrödinger-Str. 13, 67663, Kaiserslautern, Germany
- Department of Chemistry, University of Ibadan, Ibadan, 200284, Nigeria
| | - Eugenio Pérez Patallo
- Molecular Biophysics, Technische Universität Kaiserslautern (TUK), Erwin-Schrödinger-Str. 13, 67663, Kaiserslautern, Germany
| | - Annette Meister
- HALOmem and Institute of Biochemistry and Biotechnology, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Str. 3a, 06120, Halle (Saale), Germany
| | - Ritu Rajender
- Human Biology, Technische Universität Kaiserslautern (TUK), Erwin-Schrödinger-Str. 13, 67663, Kaiserslautern, Germany
| | - Stefan Kins
- Human Biology, Technische Universität Kaiserslautern (TUK), Erwin-Schrödinger-Str. 13, 67663, Kaiserslautern, Germany
| | - Markus Räschle
- Molecular Genetics, Technische Universität Kaiserslautern (TUK), Paul-Ehrlich-Str. 24, 67663, Kaiserslautern, Germany
| | - Julian Victor
- Institut für Physikalische Biologie, Heinrich-Heine-Universität Düsseldorf, Universitätsstr. 1, 40225, Düsseldorf, Germany
| | - Ci Chu
- Institut für Physikalische Biologie, Heinrich-Heine-Universität Düsseldorf, Universitätsstr. 1, 40225, Düsseldorf, Germany
| | - Manuel Etzkorn
- Institut für Physikalische Biologie, Heinrich-Heine-Universität Düsseldorf, Universitätsstr. 1, 40225, Düsseldorf, Germany
| | - Zoe Köck
- Centre for Biomolecular Magnetic Resonance, Institute for Biophysical Chemistry, Goethe University of Frankfurt/Main, Max-von-Laue-Str. 9, 60438, Frankfurt/Main, Germany
| | - Frank Bernhard
- Centre for Biomolecular Magnetic Resonance, Institute for Biophysical Chemistry, Goethe University of Frankfurt/Main, Max-von-Laue-Str. 9, 60438, Frankfurt/Main, Germany
| | | | - Carolyn Vargas
- Molecular Biophysics, Technische Universität Kaiserslautern (TUK), Erwin-Schrödinger-Str. 13, 67663, Kaiserslautern, Germany
- Biophysics, Institute of Molecular Biosciences (IMB), NAWI Graz, University of Graz, Humboldtstr. 50/III, Graz, 8010, Austria
- Field of Excellence BioHealth, University of Graz, Graz, Austria
- BioTechMed-Graz, Graz, Austria
| | - Sandro Keller
- Molecular Biophysics, Technische Universität Kaiserslautern (TUK), Erwin-Schrödinger-Str. 13, 67663, Kaiserslautern, Germany
- Biophysics, Institute of Molecular Biosciences (IMB), NAWI Graz, University of Graz, Humboldtstr. 50/III, Graz, 8010, Austria
- Field of Excellence BioHealth, University of Graz, Graz, Austria
- BioTechMed-Graz, Graz, Austria
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18
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Brady NG, Qian S, Nguyen J, O'Neill HM, Bruce BD. Small angle neutron scattering and lipidomic analysis of a native, trimeric PSI-SMALP from a thermophilic cyanobacteria. BIOCHIMICA ET BIOPHYSICA ACTA. BIOENERGETICS 2022; 1863:148596. [PMID: 35853496 PMCID: PMC10228149 DOI: 10.1016/j.bbabio.2022.148596] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2021] [Revised: 06/05/2022] [Accepted: 07/11/2022] [Indexed: 01/21/2023]
Abstract
The use of styrene-maleic acid copolymers (SMAs) to produce membrane protein-containing nanodiscs without the initial detergent isolation has gained significant interest over the last decade. We have previously shown that a Photosystem I SMALP from the thermophilic cyanobacterium, Thermosynechococcus elongatus (PSI-SMALP), has much more rapid energy transfer and charge separation in vitro than detergent isolated PSI complexes. In this study, we have utilized small-angle neutron scattering (SANS) to better understand the geometry of these SMALPs. These techniques allow us to investigate the size and shape of these particles in their fully solvated state. Further, the particle's proteolipid core and detergent shell or copolymer belt can be interrogated separately using contrast variation, a capability unique to SANS. Here we report the dimensions of the Thermosynechococcus elongatus PSI-SMALP containing a PSI trimer. At ~1.5 MDa, PSI-SMALP is the largest SMALP to be isolated; our lipidomic analysis indicates it contains ~1300 lipids/per trimeric particle, >40-fold more than the PSI-DDM particle and > 100 fold more than identified in the 1JB0 crystal structure. Interestingly, the lipid composition to the PSI trimer in the PSI-SMALP differs significantly from bulk thylakoid composition, being enriched ~50 % in the anionic sulfolipid, SQDG. Finally, utilizing the contrast match point for the SMA 1440 copolymer, we also can observe the ~1 nm SMA copolymer belt surrounding this SMALP for the first time, consistent with most models of SMA organization.
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Affiliation(s)
- Nathan G Brady
- Department of Biochemistry & Cellular and Molecular Biology, University of Tennessee, Knoxville, TN 37996, USA
| | - Shuo Qian
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA; The Second Target Station Project, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Jon Nguyen
- Department of Biochemistry & Cellular and Molecular Biology, University of Tennessee, Knoxville, TN 37996, USA
| | - Hugh M O'Neill
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Barry D Bruce
- Department of Biochemistry & Cellular and Molecular Biology, University of Tennessee, Knoxville, TN 37996, USA; Department of Chemical and Biomolecular Engineering, University of Tennessee, Knoxville, TN 37996, USA; Department of Microbiology, University of Tennessee, Knoxville, TN 37996, USA.
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19
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Nguyen THA, Le TTV, Huynh BA, Nguyen NV, Le VT, Doan VD, Tran VA, Nguyen AT, Cao XT, Vasseghian Y. Novel biogenic gold nanoparticles stabilized on poly(styrene-co-maleic anhydride) as an effective material for reduction of nitrophenols and colorimetric detection of Pb(II). ENVIRONMENTAL RESEARCH 2022; 212:113281. [PMID: 35461847 DOI: 10.1016/j.envres.2022.113281] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2022] [Revised: 04/07/2022] [Accepted: 04/08/2022] [Indexed: 06/14/2023]
Abstract
Biogenic gold nanoparticles (AuNPs) have been extensively studied for the catalytic conversion of nitrophenols (NP) into aminophenols and the colorimetric quantification of heavy metal ions in aqueous solutions. However, the high self-agglomeration ability of colloidal nanoparticles is one of the major obstacles hindering their application. In the present study, we offered novel biogenic AuNPs synthesized by a green approach using Cistanche deserticola (CD) extract as a bioreducing agent and stabilized on poly(styrene-co-maleic anhydride) (PSMA). The prepared Au@PSMA nanoparticles were characterized by various techniques (HR-TEM, SEAD, FE-SEM, DLS, TGA, XRD, and FTIR) and studied for two applications: the catalytic reduction of 3-NP by NaBH4 and the sensing detection of Pb2+ ions. The optimal conditions for the synthesis of AuNPs were investigated and established at 60 °C, 20 min, pH of 9, and 0.5 mM Au3+. Morphological studies showed that AuNPs synthesized by CD extract were mostly spherical with a mean diameter of 25 nm, while the size of polymer-integrated AuNPs was more than two-fold larger. Since PSMA acted as a matrix keeping the nanoparticles from coagulation and maintaining the optimal surface area, AuNPs integrated with PSMA showed higher catalytic efficiency with a faster reaction rate and lower activation energy than conventional nanoparticles. Au@PSMA could completely reduce 3-NP within 10 min with a rate constant of 0.127 min-1 and activation energy of 9.96 kJ/mol. The presence of PSMA also improved the stability and recyclability of AuNPs. Used as a sensor, Au@PSMA exhibited excellent sensitivity and selectivity for Pb2+ ions with a limit of detection of 0.03 μM in the linear range of 0-100 μM. The study results suggested that Au@PSMA could be used as a promising catalyst for the reduction of NP and the colorimetric sensor for detection of Pb2+ ions in aqueous environmental samples.
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Affiliation(s)
- Thi Hong Anh Nguyen
- Faculty of Chemical Engineering, Ho Chi Minh City University of Food Industry, 140 Le Trong Tan, Ho Chi Minh City, 70000, Viet Nam
| | - Thi Tuong Vy Le
- Faculty of Chemical Engineering, Industrial University of Ho Chi Minh City, Ho Chi Minh City, 70000, Viet Nam
| | - Bao An Huynh
- Faculty of Chemical Engineering, Industrial University of Ho Chi Minh City, Ho Chi Minh City, 70000, Viet Nam
| | - Ngoc Vy Nguyen
- Faculty of Chemical Engineering, Industrial University of Ho Chi Minh City, Ho Chi Minh City, 70000, Viet Nam
| | - Van Thuan Le
- Center for Advanced Chemistry, Institute of Research and Development, Duy Tan University, 03 Quang Trung, Da Nang, 55000, Viet Nam; The Faculty of Natural Sciences, Duy Tan University, 03 Quang Trung, Da Nang, 55000, Viet Nam.
| | - Van-Dat Doan
- Faculty of Chemical Engineering, Industrial University of Ho Chi Minh City, Ho Chi Minh City, 70000, Viet Nam.
| | - Vy Anh Tran
- Department of Chemical and Biochemical Engineering, Gachon University, 1342 Seongnamdaero, Sujeong-gu, Seongnam-si, 13120, Republic of Korea.
| | - Anh-Tien Nguyen
- Faculty of Chemistry, Ho Chi Minh City University of Education, 280 An Duong Vuong, Ho Chi Minh City, 70000, Viet Nam
| | - Xuan Thang Cao
- Faculty of Chemical Engineering, Industrial University of Ho Chi Minh City, Ho Chi Minh City, 70000, Viet Nam
| | - Yasser Vasseghian
- Department of Chemistry, Soongsil University, Seoul, 06978, South Korea.
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20
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van Walree CA. Intramolecular Hydrogen Bonding in DIBMA Model Compounds. MACROMOL THEOR SIMUL 2022. [DOI: 10.1002/mats.202200042] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Cornelis A. van Walree
- Membrane Biochemistry and Biophysics Utrecht University Padualaan 8 Utrecht 3584 CH Netherlands
- University College Utrecht Campusplein 1 Utrecht 3584 ED the Netherlands
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21
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Janata M, Čadová E, Angelisová P, Charnavets T, Hořejší V, Raus V. Tailoring Butyl Methacrylate/Methacrylic Acid Copolymers for the Solubilization of Membrane Proteins: The Influence of Composition and Molecular Weight. Macromol Biosci 2022; 22:e2200284. [PMID: 35964154 DOI: 10.1002/mabi.202200284] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Revised: 08/02/2022] [Indexed: 11/11/2022]
Abstract
Low-molecular weight (MW) amphiphilic copolymers have been recently introduced as a powerful tool for the detergent-free isolation of cell membrane proteins. Herein, we use a screening approach to identify a new copolymer type for this application. Via a two-step ATRP/acidolysis procedure, we prepare a 3×3 matrix of well-defined poly[(butyl methacrylate)-co-(methacrylic acid)] copolymers (denoted BMAA) differing in their MW and ratio of hydrophobic (BMA) and hydrophilic (MAA) units. Subsequently, using the biologically relevant model (T-cell line Jurkat), we identify two compositions of BMAA copolymers that solubilize cell membranes to an extent comparable to the industry standard, styrene-maleic acid copolymer (SMA), while avoiding the potentially problematic phenyl groups. Surprisingly, while only the lowest-MW variant of the BMA/MAA 2:1 composition is effective, all the copolymers of the BMA/MAA 1:1 composition are found to solubilize the model membranes, including the high-MW variant (MW of 14 000). Importantly, the density gradient ultracentrifugation/SDS PAGE/Western blotting experiments reveal that the BMA/MAA 1:1 copolymers disintegrate the Jurkat membranes differently than SMA, as demonstrated by the different distribution patterns of two tested membrane protein markers. This makes the BMAA copolymers a useful tool for studies on membrane microdomains differing in their composition and resistance to membrane-disintegrating polymers. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Miroslav Janata
- Institute of Macromolecular Chemistry, Czech Academy of Sciences, Heyrovského nám. 2, Prague 6, 162 06, Czech Republic
| | - Eva Čadová
- Institute of Macromolecular Chemistry, Czech Academy of Sciences, Heyrovského nám. 2, Prague 6, 162 06, Czech Republic
| | - Pavla Angelisová
- Institute of Molecular Genetics of the Czech Academy of Sciences, Vídeňská 1083, Prague 4, 142 20, Czech Republic
| | - Tatsiana Charnavets
- Institute of Molecular Genetics of the Czech Academy of Sciences, Vídeňská 1083, Prague 4, 142 20, Czech Republic.,T. Charnavets, Institute of Biotechnology of the Czech Academy of Sciences, BIOCEV, Průmyslová 595, Vestec, CZ-25242, Czech Republic
| | - Václav Hořejší
- Institute of Molecular Genetics of the Czech Academy of Sciences, Vídeňská 1083, Prague 4, 142 20, Czech Republic
| | - Vladimír Raus
- Institute of Macromolecular Chemistry, Czech Academy of Sciences, Heyrovského nám. 2, Prague 6, 162 06, Czech Republic
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22
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Tanaka M. Applications of Synthetic Polymer Discoidal Lipid Nanoparticles to Biomedical Research. Chem Pharm Bull (Tokyo) 2022; 70:507-513. [DOI: 10.1248/cpb.c22-00125] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- Masafumi Tanaka
- Laboratory of Functional Molecular Chemistry, Kobe Pharmaceutical University
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23
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The function of BK channels extracted and purified within SMALPs. Biochem J 2022; 479:1609-1619. [PMID: 35851603 PMCID: PMC9444072 DOI: 10.1042/bcj20210628] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 06/27/2022] [Accepted: 07/19/2022] [Indexed: 11/17/2022]
Abstract
Human BK channels are large voltage and Ca2+-activated K+ channels, involved in several important functions within the body. The core channel is a tetramer of α subunits, and its function is modulated by the presence of β and γ accessory subunits. BK channels composed of α subunits, as well as BK channels composed of α and β1 subunits, were successfully solubilised from HEK cells with styrene maleic acid (SMA) polymer and purified by nickel affinity chromatography. Native SMA–PAGE analysis of the purified proteins showed the α subunits were extracted as a tetramer. In the presence of β1 subunits, they were co-extracted with the α subunits as a heteromeric complex. Purified SMA lipid particles (SMALPs) containing BK channel could be inserted into planar lipid bilayers (PLB) and single channel currents recorded, showing a high conductance (≈260 pS), as expected. The open probability was increased in the presence of co-purified β1 subunits. However, voltage-dependent gating of the channel was restricted. In conclusion, we have demonstrated that SMA can be used to effectively extract and purify large, complex, human ion channels, from low expressing sources. That these large channels can be incorporated into PLB from SMALPs and display voltage-dependent channel activity. However, the SMA appears to reduce the voltage dependent gating of the channels.
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24
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Neville GM, Edler KJ, Price GJ. Fluorescent styrene maleic acid copolymers to facilitate membrane protein studies in lipid nanodiscs. NANOSCALE 2022; 14:5689-5693. [PMID: 35315461 DOI: 10.1039/d1nr07230g] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Fluorescently-labelled variants of poly(styrene-co-maleic acid), SMA, have been synthesised by RAFT copolymerisation. We show that low ratios of vinyl fluorophores, analogous to styrene, can be successfully incorporated during polymerisation without detriment to nanodisc formation upon interaction with lipids. These novel copolymers are capable of encapuslating lipids and the model membrane protein, gramicidin, and hence have the potential to be applied in fluorescence-based biological studies. To demonstrate this, energy transfer is used to probe polymer-protein interactions in nanodiscs. The copolymers may also be used to monitor nanodisc self assembly by exploiting aggregation-caused-quenching (ACQ).
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Affiliation(s)
| | - Karen J Edler
- Department of Chemistry, University of Bath, Bath, BA2 7AY, UK
| | - Gareth J Price
- Department of Chemistry, University of Bath, Bath, BA2 7AY, UK
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25
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Hall SCL, Tognoloni C, Campbell RA, Richens J, O'Shea P, Terry AE, Price GJ, Dafforn TR, Edler KJ, Arnold T. The interaction of styrene maleic acid copolymers with phospholipids in Langmuir monolayers, vesicles and nanodiscs; a structural study. J Colloid Interface Sci 2022; 625:220-236. [PMID: 35716617 DOI: 10.1016/j.jcis.2022.03.102] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Revised: 03/21/2022] [Accepted: 03/22/2022] [Indexed: 10/31/2022]
Abstract
HYPOTHESIS Self-assembly of amphipathic styrene maleic acid copolymers with phospholipids in aqueous solution results in the formation of 'nanodiscs' containing a planar segment of phospholipid bilayer encapsulated by a polymer belt. Recently, studies have reported that lipids rapidly exchange between both nanodiscs in solution and external sources of lipids. Outstanding questions remain regarding details of polymer-lipid interactions, factors influencing lipid exchange and structural effects of such exchange processes. Here, the dynamic behaviour of nanodiscs is investigated, specifically the role of membrane charge and polymer chemistry. EXPERIMENTS Two model systems are investigated: fluorescently labelled phospholipid vesicles, and Langmuir monolayers of phospholipids. Using fluorescence spectroscopy and time-resolved neutron reflectometry, the membrane potential, monolayer structure and composition are monitored with respect to time upon polymer and nanodisc interactions. FINDINGS In the presence of external lipids, polymer chains embed throughout lipid membranes, the extent of which is governed by the net membrane charge. Nanodiscs stabilised by three different polymers will all exchange lipids and polymer with monolayers to differing extents, related to the properties of the stabilising polymer belt. These results demonstrate the dynamic nature of nanodiscs which interact with the local environment and are likely to deposit both lipids and polymer at all stages of use.
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Affiliation(s)
- Stephen C L Hall
- School of Biosciences, University of Birmingham, Edgbaston, B15 2TT, UK; Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 ODE, UK; ISIS Neutron and Muon Source, Rutherford Appleton Laboratory, Didcot OX11 0QX, UK.
| | - Cecilia Tognoloni
- Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, UK
| | - Richard A Campbell
- Institut Laue-Langevin, 71 Avenue des Martyrs, 38042 Grenoble, France; Division of Pharmacy and Optometry, University of Manchester, Manchester M13 9PT, UK
| | - Joanna Richens
- School of Life Sciences, University of Nottingham, Nottingham NG7 2RD, UK
| | - Paul O'Shea
- School of Life Sciences, University of Nottingham, Nottingham NG7 2RD, UK; Biomedical and Life Sciences, Lancaster University, Lancaster LA1 4YG, UK
| | - Ann E Terry
- MAX IV Laboratory, Lund University, SE-221 00 Lund, Sweden
| | - Gareth J Price
- Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, UK
| | - Tim R Dafforn
- School of Biosciences, University of Birmingham, Edgbaston, B15 2TT, UK
| | - Karen J Edler
- Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, UK
| | - Thomas Arnold
- ISIS Neutron and Muon Source, Rutherford Appleton Laboratory, Didcot OX11 0QX, UK; ISIS Neutron and Muon Source, Rutherford Appleton Laboratory, Didcot OX11 0QX, UK; Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, UK; European Spallation Source ERIC, P.O Box 176, SE-221 00 Lund, Sweden
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26
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Vallejo DD, Rojas Ramírez C, Parson KF, Han Y, Gadkari VV, Ruotolo BT. Mass Spectrometry Methods for Measuring Protein Stability. Chem Rev 2022; 122:7690-7719. [PMID: 35316030 DOI: 10.1021/acs.chemrev.1c00857] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Mass spectrometry is a central technology in the life sciences, providing our most comprehensive account of the molecular inventory of the cell. In parallel with developments in mass spectrometry technologies targeting such assessments of cellular composition, mass spectrometry tools have emerged as versatile probes of biomolecular stability. In this review, we cover recent advancements in this branch of mass spectrometry that target proteins, a centrally important class of macromolecules that accounts for most biochemical functions and drug targets. Our efforts cover tools such as hydrogen-deuterium exchange, chemical cross-linking, ion mobility, collision induced unfolding, and other techniques capable of stability assessments on a proteomic scale. In addition, we focus on a range of application areas where mass spectrometry-driven protein stability measurements have made notable impacts, including studies of membrane proteins, heat shock proteins, amyloidogenic proteins, and biotherapeutics. We conclude by briefly discussing the future of this vibrant and fast-moving area of research.
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Affiliation(s)
- Daniel D Vallejo
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Carolina Rojas Ramírez
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Kristine F Parson
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Yilin Han
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Varun V Gadkari
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Brandon T Ruotolo
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
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27
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Morrison KA, Wood L, Edler KJ, Doutch J, Price GJ, Koumanov F, Whitley P. Membrane extraction with styrene-maleic acid copolymer results in insulin receptor autophosphorylation in the absence of ligand. Sci Rep 2022; 12:3532. [PMID: 35241773 PMCID: PMC8894449 DOI: 10.1038/s41598-022-07606-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2021] [Accepted: 02/21/2022] [Indexed: 11/09/2022] Open
Abstract
Extraction of integral membrane proteins with poly(styrene-co-maleic acid) provides a promising alternative to detergent extraction. A major advantage of extraction using copolymers rather than detergent is the retention of the lipid bilayer around the proteins. Here we report the first functional investigation of the mammalian insulin receptor which was extracted from cell membranes using poly(styrene-co-maleic acid). We found that the copolymer efficiently extracted the insulin receptor from 3T3L1 fibroblast membranes. Surprisingly, activation of the insulin receptor and proximal downstream signalling was detected upon copolymer extraction even in the absence of insulin stimulation. Insulin receptor and IRS1 phosphorylations were above levels measured in the control extracts made with detergents. However, more distal signalling events in the insulin signalling cascade, such as the phosphorylation of Akt were not observed. Following copolymer extraction, in vitro addition of insulin had no further effect on insulin receptor or IRS1 phosphorylation. Therefore, under our experimental conditions, the insulin receptor is not functionally responsive to insulin. This study is the first to investigate receptor tyrosine kinases extracted from mammalian cells using a styrene-maleic acid copolymer and highlights the importance of thorough functional characterisation when using this method of protein extraction.
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Affiliation(s)
- Kerrie A Morrison
- Department of Biology and Biochemistry, University of Bath, Bath, UK.,Department of Chemistry, University of Bath, Bath, UK.,Centre for Sustainable Circular Technologies, University of Bath, Bath, UK
| | - Laura Wood
- Department of Biology and Biochemistry, University of Bath, Bath, UK.,Department for Health, Centre for Nutrition, Exercise and Metabolism, University of Bath, Bath, UK
| | - Karen J Edler
- Department of Chemistry, University of Bath, Bath, UK
| | - James Doutch
- ISIS Pulsed Neutron and Muon Source, Rutherford Appleton Laboratory, Harwell Oxford, Didcot, OX11 0QX, UK
| | - Gareth J Price
- Department of Chemistry, University of Bath, Bath, UK.,Department of Chemistry, Khalifa University, Abu Dhabi, UAE
| | - Francoise Koumanov
- Department for Health, Centre for Nutrition, Exercise and Metabolism, University of Bath, Bath, UK.
| | - Paul Whitley
- Department of Biology and Biochemistry, University of Bath, Bath, UK.
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28
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Jeong C, Franklin R, Edler KJ, Vanommeslaeghe K, Krueger S, Curtis JE. Styrene-Maleic Acid Copolymer Nanodiscs to Determine the Shape of Membrane Proteins. J Phys Chem B 2022; 126:1034-1044. [PMID: 35089036 DOI: 10.1021/acs.jpcb.1c05050] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Lipid nanodiscs can be used to solubilize functional membrane proteins (MPs) in nativelike environments. Thus, they are promising reagents that have been proven useful to characterize MPs. Both protein and non-protein molecular belts have shown promise to maintain the structural integrity of MPs in lipid nanodiscs. Small-angle neutron scattering (SANS) can be used to determine low-resolution structures of proteins in solution, which can be enhanced through the use of contrast variation methods. We present theoretical contrast variation SANS results for protein and styrene-maleic acid copolymer (SMA) belt 1,2-dimyristoyl-sn-glycero-3-phosphorylcholine (DMPC) nanodiscs with and without additional bound or transmembrane proteins. The predicted scattering properties are derived from atomistic molecular dynamics simulations to account for conformational fluctuations, and we determine deuterium-labeling conditions such that SANS intensity profiles only include contributions from the scattering of the MP of interest. We propose strategies to tune the neutron scattering length densities (SLDs) of the SMA and DMPC using selective deuterium labeling such that the SLD of the nanodisc becomes homogeneous and its scattering can essentially be eliminated in solvents containing an appropriate amount of D2O. These finely tuned labeled polymer-based nanodiscs are expected to be useful to extract the size and molecular shape information of MPs using SANS-based contrast variation experiments, and they can be used with MPs of any molecular weight.
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Affiliation(s)
- Cheol Jeong
- NIST Center for Neutron Research, National Institute of Standards and Technology, 100 Bureau Drive, Mail Stop 6102, Gaithersburg, Maryland 20899, United States.,Department of Chemistry, The University of Tennessee, Knoxville, Tennessee 37996-1600, United States
| | - Ryan Franklin
- NIST Center for Neutron Research, National Institute of Standards and Technology, 100 Bureau Drive, Mail Stop 6102, Gaithersburg, Maryland 20899, United States
| | - Karen J Edler
- Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, U.K
| | - Kenno Vanommeslaeghe
- Department of Analytical Chemistry, Applied Chemometrics and Molecular Modelling─FABI, Vrije Universiteit Brussel (VUB), Laarbeeklaan 103, 1090 Brussels, Belgium
| | - Susan Krueger
- NIST Center for Neutron Research, National Institute of Standards and Technology, 100 Bureau Drive, Mail Stop 6102, Gaithersburg, Maryland 20899, United States
| | - Joseph E Curtis
- NIST Center for Neutron Research, National Institute of Standards and Technology, 100 Bureau Drive, Mail Stop 6102, Gaithersburg, Maryland 20899, United States
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29
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Orekhov PS, Bozdaganyan ME, Voskoboynikova N, Mulkidjanian AY, Karlova MG, Yudenko A, Remeeva A, Ryzhykau YL, Gushchin I, Gordeliy VI, Sokolova OS, Steinhoff HJ, Kirpichnikov MP, Shaitan KV. Mechanisms of Formation, Structure, and Dynamics of Lipoprotein Discs Stabilized by Amphiphilic Copolymers: A Comprehensive Review. NANOMATERIALS 2022; 12:nano12030361. [PMID: 35159706 PMCID: PMC8838559 DOI: 10.3390/nano12030361] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/19/2021] [Revised: 01/15/2022] [Accepted: 01/20/2022] [Indexed: 12/16/2022]
Abstract
Amphiphilic copolymers consisting of alternating hydrophilic and hydrophobic units account for a major recent methodical breakthrough in the investigations of membrane proteins. Styrene–maleic acid (SMA), diisobutylene–maleic acid (DIBMA), and related copolymers have been shown to extract membrane proteins directly from lipid membranes without the need for classical detergents. Within the particular experimental setup, they form disc-shaped nanoparticles with a narrow size distribution, which serve as a suitable platform for diverse kinds of spectroscopy and other biophysical techniques that require relatively small, homogeneous, water-soluble particles of separate membrane proteins in their native lipid environment. In recent years, copolymer-encased nanolipoparticles have been proven as suitable protein carriers for various structural biology applications, including cryo-electron microscopy (cryo-EM), small-angle scattering, and conventional and single-molecule X-ray diffraction experiments. Here, we review the current understanding of how such nanolipoparticles are formed and organized at the molecular level with an emphasis on their chemical diversity and factors affecting their size and solubilization efficiency.
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Affiliation(s)
- Philipp S. Orekhov
- Faculty of Biology, Lomonosov Moscow State University, 119991 Moscow, Russia; (M.E.B.); (M.G.K.); (O.S.S.); (M.P.K.)
- Faculty of Biology, Shenzhen MSU-BIT University, Shenzhen 518172, China
- Institute of Personalized Medicine, Sechenov University, 119146 Moscow, Russia
- Correspondence: (P.S.O.); (K.V.S.)
| | - Marine E. Bozdaganyan
- Faculty of Biology, Lomonosov Moscow State University, 119991 Moscow, Russia; (M.E.B.); (M.G.K.); (O.S.S.); (M.P.K.)
- Faculty of Biology, Shenzhen MSU-BIT University, Shenzhen 518172, China
- N.N. Semenov Federal Research Center for Chemical Physics, Russian Academy of Sciences, 119991 Moscow, Russia
| | - Natalia Voskoboynikova
- Department of Physics, University of Osnabrück, Barbarastrasse 7, 49076 Osnabrück, Germany; (N.V.); (A.Y.M.); (H.-J.S.)
| | - Armen Y. Mulkidjanian
- Department of Physics, University of Osnabrück, Barbarastrasse 7, 49076 Osnabrück, Germany; (N.V.); (A.Y.M.); (H.-J.S.)
- Faculty of Bioengineering and Bioinformatics and Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119234 Moscow, Russia
| | - Maria G. Karlova
- Faculty of Biology, Lomonosov Moscow State University, 119991 Moscow, Russia; (M.E.B.); (M.G.K.); (O.S.S.); (M.P.K.)
| | - Anna Yudenko
- Research Center for Molecular Mechanisms of Aging and Age-Related Diseases, Moscow Institute of Physics and Technology, 141700 Dolgoprudny, Russia; (A.Y.); (A.R.); (Y.L.R.); (I.G.); (V.I.G.)
| | - Alina Remeeva
- Research Center for Molecular Mechanisms of Aging and Age-Related Diseases, Moscow Institute of Physics and Technology, 141700 Dolgoprudny, Russia; (A.Y.); (A.R.); (Y.L.R.); (I.G.); (V.I.G.)
| | - Yury L. Ryzhykau
- Research Center for Molecular Mechanisms of Aging and Age-Related Diseases, Moscow Institute of Physics and Technology, 141700 Dolgoprudny, Russia; (A.Y.); (A.R.); (Y.L.R.); (I.G.); (V.I.G.)
| | - Ivan Gushchin
- Research Center for Molecular Mechanisms of Aging and Age-Related Diseases, Moscow Institute of Physics and Technology, 141700 Dolgoprudny, Russia; (A.Y.); (A.R.); (Y.L.R.); (I.G.); (V.I.G.)
| | - Valentin I. Gordeliy
- Research Center for Molecular Mechanisms of Aging and Age-Related Diseases, Moscow Institute of Physics and Technology, 141700 Dolgoprudny, Russia; (A.Y.); (A.R.); (Y.L.R.); (I.G.); (V.I.G.)
- Institute of Biological Information Processing (IBI-7: Structural Biochemistry), Forschungszentrum Jülich, 52428 Jülich, Germany
- Institut de Biologie Structurale J.-P. Ebel, Université Grenoble Alpes-CEA-CNRS, 38000 Grenoble, France
- JuStruct: Jülich Center for Structural Biology, Forschungszentrum Jülich, 52428 Jülich, Germany
| | - Olga S. Sokolova
- Faculty of Biology, Lomonosov Moscow State University, 119991 Moscow, Russia; (M.E.B.); (M.G.K.); (O.S.S.); (M.P.K.)
- Faculty of Biology, Shenzhen MSU-BIT University, Shenzhen 518172, China
| | - Heinz-Jürgen Steinhoff
- Department of Physics, University of Osnabrück, Barbarastrasse 7, 49076 Osnabrück, Germany; (N.V.); (A.Y.M.); (H.-J.S.)
| | - Mikhail P. Kirpichnikov
- Faculty of Biology, Lomonosov Moscow State University, 119991 Moscow, Russia; (M.E.B.); (M.G.K.); (O.S.S.); (M.P.K.)
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 117997 Moscow, Russia
| | - Konstantin V. Shaitan
- Faculty of Biology, Lomonosov Moscow State University, 119991 Moscow, Russia; (M.E.B.); (M.G.K.); (O.S.S.); (M.P.K.)
- Correspondence: (P.S.O.); (K.V.S.)
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30
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Broadbent L, Depping P, Lodé A, Vaitsopoulou A, Hardy D, Ayub H, Mitchell-White J, Kerr ID, Goddard AD, Bill RM, Rothnie AJ. Detergent-Free Membrane Protein Purification Using SMA Polymer. Methods Mol Biol 2022; 2507:389-404. [PMID: 35773594 DOI: 10.1007/978-1-0716-2368-8_21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
One of the big challenges for the study of structure and function of membrane proteins is the need to extract them from the membrane. Traditionally this was achieved using detergents which disrupt the membrane and form a micelle around the protein, but this can cause issues with protein function and/or stability. In 2009 an alternative approach was reported, using styrene maleic acid (SMA) copolymer to extract small discs of lipid bilayer encapsulated by the polymer and termed SMALPs (SMA lipid particles). Since then this approach has been shown to work for a range of different proteins from many different expression systems. It allows the extraction and purification of a target protein while maintaining a lipid bilayer environment. Recently this has led to several new high-resolution structures and novel insights to function. As with any method there are some limitations and issues to be aware of. Here we describe a standard protocol for preparation of the polymer and its use for membrane protein purification, and also include details of typical challenges that may be encountered and possible ways to address those.
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Affiliation(s)
- Luke Broadbent
- College of Health & Life Sciences, Aston University, Birmingham, UK
| | - Peer Depping
- College of Health & Life Sciences, Aston University, Birmingham, UK
| | - Alexis Lodé
- College of Health & Life Sciences, Aston University, Birmingham, UK
| | | | - David Hardy
- College of Health & Life Sciences, Aston University, Birmingham, UK
- School of Biosciences, University of Birmingham, Birmingham, UK
| | - Hoor Ayub
- College of Health & Life Sciences, Aston University, Birmingham, UK
- Faculty of Health & Life Sciences, Coventry University, Coventry, UK
| | - James Mitchell-White
- School of Life Sciences, University of Nottingham Medical School, Queen's Medical Centre, Nottingham, UK
| | - Ian D Kerr
- School of Life Sciences, University of Nottingham Medical School, Queen's Medical Centre, Nottingham, UK
| | - Alan D Goddard
- College of Health & Life Sciences, Aston University, Birmingham, UK
| | - Roslyn M Bill
- College of Health & Life Sciences, Aston University, Birmingham, UK
| | - Alice J Rothnie
- College of Health & Life Sciences, Aston University, Birmingham, UK.
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31
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Morrison KA, Doekhie A, Neville GM, Price GJ, Whitley P, Doutch J, Edler KJ. Ab initio reconstruction of small angle scattering data for membrane proteins in copolymer nanodiscs. BBA ADVANCES 2022; 2:100033. [PMID: 37082608 PMCID: PMC10074903 DOI: 10.1016/j.bbadva.2021.100033] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Background Small angle scattering techniques are beginning to be more widely utilised for structural analysis of biological systems. However, applying these techniques to study membrane proteins still remains problematic, due to sample preparation requirements and analysis of the resulting data. The development of styrene-maleic acid co-polymers (SMA) to extract membrane proteins into nanodiscs for further study provides a suitable environment for structural analysis. Methods We use small angle neutron scattering (SANS) with three different contrasts to determine structural information for two different polymer nanodisc-incorporated proteins, Outer membrane protein F (OmpF) and gramicidin. Ab initio modelling was applied to generate protein/lipid structures from the SANS data. Other complementary structural methodologies, such as DLS, CD and TEM were compared alongside this data with known protein crystal structures. Results A single-phase model was constructed for gramicidin-containing nanodiscs, which showed dimer formation in the centre of the nanodisc. For OmpF-nanodiscs we were able to construct a multi-phase model, providing structural information on the protein/lipid and polymer components of the sample. Conclusions Polymer-nanodiscs can provide a suitable platform to investigate certain membrane proteins using SANS, alongside other structural methodologies. However, differences between the published crystal structure and OmpF-nanodiscs were observed, suggesting the nanodisc structure could be altering the folding of the protein. General significance Small angle scattering techniques can provide structural information on the protein and polymer nanodisc without requiring crystallisation of the protein. Additional complementary techniques, such as ab initio modelling, can generate alternative models both the protein and nanodisc system.
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Affiliation(s)
- Kerrie A. Morrison
- Department of Chemistry, University of Bath, Bath, UK
- Department of Biology and Biochemistry, University of Bath, Bath, UK
- Centre for Sustainable and Circular Technologies, University of Bath, Bath, UK
| | - Aswin Doekhie
- Department of Chemistry, University of Bath, Bath, UK
| | - George M. Neville
- Department of Chemistry, University of Bath, Bath, UK
- Centre for Sustainable and Circular Technologies, University of Bath, Bath, UK
| | - Gareth J. Price
- Department of Chemistry, University of Bath, Bath, UK
- Department of Chemistry, Khalifa University, Abu Dhabi, UAE
| | - Paul Whitley
- Department of Biology and Biochemistry, University of Bath, Bath, UK
| | - James Doutch
- ISIS Pulsed Neutron and Muon Source, Rutherford Appleton Laboratory, Harwell Oxford, Didcot OX11 0QX. UK
- Corresponding authors.
| | - Karen J. Edler
- Department of Chemistry, University of Bath, Bath, UK
- Corresponding authors.
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32
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Dimitrova VS, Song S, Karagiaridi A, Marand A, Pinkett HW. Detergent Alternatives: Membrane Protein Purification Using Synthetic Nanodisc Polymers. Methods Mol Biol 2022; 2507:375-387. [PMID: 35773593 PMCID: PMC9361707 DOI: 10.1007/978-1-0716-2368-8_20] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
The development of styrene maleic acid (SMA) and diisobutylene maleic acid (DIBMA) copolymers provides an alternative to traditional detergent extraction of integral membrane proteins. By inserting into the membrane, these polymers can extract membrane proteins along with lipids in the form of native nanodiscs made by poly(styrene co-maleic anhydride) derivatives. Unlike detergent solubilization, where membrane proteins may lose annular lipids necessary for proper folding and stability, native nanodiscs allow for proteins to reside in the natural lipid environment. In addition, polymer-based nanodiscs can be purified using common chromatography methods similar to protocols established with detergent solubilization purification. Here we describe the solubilization screening and purification of an integral membrane protein using several commercial copolymers.
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Affiliation(s)
| | - Saemee Song
- Department of Molecular Biosciences, Northwestern University, Evanston, IL, USA
- Department of Infectious Diseases Research, Korea Research Institute of Chemical Technology, Daejeon, South Korea
| | | | - Anika Marand
- Department of Molecular Biosciences, Northwestern University, Evanston, IL, USA
| | - Heather W Pinkett
- Department of Molecular Biosciences, Northwestern University, Evanston, IL, USA.
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33
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Hawkins OP, Jahromi CPT, Gulamhussein AA, Nestorow S, Bahra T, Shelton C, Owusu-Mensah QK, Mohiddin N, O'Rourke H, Ajmal M, Byrnes K, Khan M, Nahar NN, Lim A, Harris C, Healy H, Hasan SW, Ahmed A, Evans L, Vaitsopoulou A, Akram A, Williams C, Binding J, Thandi RK, Joby A, Guest A, Tariq MZ, Rasool F, Cavanagh L, Kang S, Asparuhov B, Jestin A, Dafforn TR, Simms J, Bill RM, Goddard AD, Rothnie AJ. Membrane protein extraction and purification using partially-esterified SMA polymers. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2021; 1863:183758. [PMID: 34480878 PMCID: PMC8484863 DOI: 10.1016/j.bbamem.2021.183758] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/09/2021] [Revised: 08/16/2021] [Accepted: 08/24/2021] [Indexed: 12/15/2022]
Abstract
Styrene maleic acid (SMA) polymers have proven to be very successful for the extraction of membrane proteins, forming SMA lipid particles (SMALPs), which maintain a lipid bilayer around the membrane protein. SMALP-encapsulated membrane proteins can be used for functional and structural studies. The SMALP approach allows retention of important protein-annular lipid interactions, exerts lateral pressure, and offers greater stability than traditional detergent solubilisation. However, SMA polymer does have some limitations, including a sensitivity to divalent cations and low pH, an absorbance spectrum that overlaps with many proteins, and possible restrictions on protein conformational change. Various modified polymers have been developed to try to overcome these challenges, but no clear solution has been found. A series of partially-esterified variants of SMA (SMA 2625, SMA 1440 and SMA 17352) has previously been shown to be highly effective for solubilisation of plant and cyanobacterial thylakoid membranes. It was hypothesised that the partial esterification of maleic acid groups would increase tolerance to divalent cations. Therefore, these partially-esterified polymers were tested for the solubilisation of lipids and membrane proteins, and their tolerance to magnesium ions. It was found that all partially esterified polymers were capable of solubilising and purifying a range of membrane proteins, but the yield of protein was lower with SMA 1440, and the degree of purity was lower for both SMA 1440 and SMA 17352. SMA 2625 performed comparably to SMA 2000. SMA 1440 also showed an increased sensitivity to divalent cations. Thus, it appears the interactions between SMA and divalent cations are more complex than proposed and require further investigation.
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Affiliation(s)
- Olivia P Hawkins
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | | | - Aiman A Gulamhussein
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Stephanie Nestorow
- School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
| | - Taranpreet Bahra
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Christian Shelton
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Quincy K Owusu-Mensah
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Naadiya Mohiddin
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Hannah O'Rourke
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Mariam Ajmal
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Kara Byrnes
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Madiha Khan
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Nila N Nahar
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Arcella Lim
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Cassandra Harris
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Hannah Healy
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Syeda W Hasan
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Asma Ahmed
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Lora Evans
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Afroditi Vaitsopoulou
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Aneel Akram
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Chris Williams
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Johanna Binding
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Rumandeep K Thandi
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Aswathy Joby
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Ashley Guest
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Mohammad Z Tariq
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Farah Rasool
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Luke Cavanagh
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Simran Kang
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Biser Asparuhov
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Aleksandr Jestin
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Timothy R Dafforn
- School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
| | - John Simms
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Roslyn M Bill
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Alan D Goddard
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Alice J Rothnie
- College of Health & Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK.
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34
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Higgins AJ, Flynn AJ, Marconnet A, Musgrove LJ, Postis VLG, Lippiat JD, Chung CW, Ceska T, Zoonens M, Sobott F, Muench SP. Cycloalkane-modified amphiphilic polymers provide direct extraction of membrane proteins for CryoEM analysis. Commun Biol 2021; 4:1337. [PMID: 34824357 PMCID: PMC8617058 DOI: 10.1038/s42003-021-02834-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Accepted: 10/27/2021] [Indexed: 12/30/2022] Open
Abstract
Membrane proteins are essential for cellular growth, signalling and homeostasis, making up a large proportion of therapeutic targets. However, the necessity for a solubilising agent to extract them from the membrane creates challenges in their structural and functional study. Although amphipols have been very effective for single-particle electron cryo-microscopy (cryoEM) and mass spectrometry, they rely on initial detergent extraction before exchange into the amphipol environment. Therefore, circumventing this pre-requirement would be a big advantage. Here we use an alternative type of amphipol: a cycloalkane-modified amphiphile polymer (CyclAPol) to extract Escherichia coli AcrB directly from the membrane and demonstrate that the protein can be isolated in a one-step purification with the resultant cryoEM structure achieving 3.2 Å resolution. Together this work shows that cycloalkane amphipols provide a powerful approach for the study of membrane proteins, allowing native extraction and high-resolution structure determination by cryoEM.
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Affiliation(s)
- Anna J Higgins
- School of Biomedical Sciences, Faculty of Biological Sciences & Astbury Centre for Structural and Molecular Biology, University of Leeds, Leeds, LS2 9JT, UK
| | - Alex J Flynn
- School of Biomedical Sciences, Faculty of Biological Sciences & Astbury Centre for Structural and Molecular Biology, University of Leeds, Leeds, LS2 9JT, UK
| | - Anaïs Marconnet
- Université de Paris, Laboratoire de Biologie Physico-Chimique des Protéines Membranaires, CNRS, UMR 7099, F-75005, Paris, France
- Institut de Biologie Physico-Chimique, Fondation Edmond de Rothschild pour le dévelopement de la recherche scientifique, F-75005, Paris, France
| | - Laura J Musgrove
- School of Biomedical Sciences, Faculty of Biological Sciences & Astbury Centre for Structural and Molecular Biology, University of Leeds, Leeds, LS2 9JT, UK
| | - Vincent L G Postis
- School of Biomedical Sciences, Faculty of Biological Sciences & Astbury Centre for Structural and Molecular Biology, University of Leeds, Leeds, LS2 9JT, UK
- Wellcome Centre for Anti-Infectives Research, Drug Discovery Unit, Division of Biological Chemistry and Drug Discovery, University of Dundee, Dundee, DD1 5EH, UK
| | - Jonathan D Lippiat
- School of Biomedical Sciences, Faculty of Biological Sciences & Astbury Centre for Structural and Molecular Biology, University of Leeds, Leeds, LS2 9JT, UK
| | - Chun-Wa Chung
- GlaxoSmithKline, Gunnels Wood Road, Stevenage, SG1 2NY, UK
| | | | - Manuela Zoonens
- Université de Paris, Laboratoire de Biologie Physico-Chimique des Protéines Membranaires, CNRS, UMR 7099, F-75005, Paris, France.
- Institut de Biologie Physico-Chimique, Fondation Edmond de Rothschild pour le dévelopement de la recherche scientifique, F-75005, Paris, France.
| | - Frank Sobott
- School of Molecular and Cellular Biology, Faculty of Biological Sciences & Astbury Centre for Structural and Molecular Biology, University of Leeds, Leeds, LS2 9JT, UK.
| | - Stephen P Muench
- School of Biomedical Sciences, Faculty of Biological Sciences & Astbury Centre for Structural and Molecular Biology, University of Leeds, Leeds, LS2 9JT, UK.
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35
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Abstract
The SARS-CoV-2 coronavirus, the etiologic agent of COVID-19, uses its spike (S) glycoprotein anchored in the viral membrane to enter host cells. The S glycoprotein is the major target for neutralizing antibodies elicited by natural infection and by vaccines. Approximately 35% of the SARS-CoV-2 S glycoprotein consists of carbohydrate, which can influence virus infectivity and susceptibility to antibody inhibition. We found that virus-like particles produced by coexpression of SARS-CoV-2 S, M, E, and N proteins contained spike glycoproteins that were extensively modified by complex carbohydrates. We used a fucose-selective lectin to purify the Golgi-modified fraction of a wild-type SARS-CoV-2 S glycoprotein trimer and determined its glycosylation and disulfide bond profile. Compared with soluble or solubilized S glycoproteins modified to prevent proteolytic cleavage and to retain a prefusion conformation, more of the wild-type S glycoprotein N-linked glycans are processed to complex forms. Even Asn 234, a significant percentage of which is decorated by high-mannose glycans on other characterized S trimer preparations, is predominantly modified in the Golgi compartment by processed glycans. Three incompletely occupied sites of O-linked glycosylation were detected. Viruses pseudotyped with natural variants of the serine/threonine residues implicated in O-linked glycosylation were generally infectious and exhibited sensitivity to neutralization by soluble ACE2 and convalescent antisera comparable to that of the wild-type virus. Unlike other natural cysteine variants, a Cys15Phe (C15F) mutant retained partial, but unstable, infectivity. These findings enhance our understanding of the Golgi processing of the native SARS-CoV-2 S glycoprotein carbohydrates and could assist the design of interventions. IMPORTANCE The SARS-CoV-2 coronavirus, which causes COVID-19, uses its spike glycoprotein to enter host cells. The viral spike glycoprotein is the main target of host neutralizing antibodies that help to control SARS-CoV-2 infection and are important for the protection provided by vaccines. The SARS-CoV-2 spike glycoprotein consists of a trimer of two subunits covered with a coat of carbohydrates (sugars). Here, we describe the disulfide bonds that assist the SARS-CoV-2 spike glycoprotein to assume the correct shape and the composition of the sugar moieties on the glycoprotein surface. We also evaluate the consequences of natural virus variation in O-linked sugar addition and in the cysteine residues involved in disulfide bond formation. This information can expedite the improvement of vaccines and therapies for COVID-19.
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36
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Morrison KA, Heesom KJ, Edler KJ, Doutch J, Price GJ, Koumanov F, Whitley P. Development of Methodology to Investigate the Surface SMALPome of Mammalian Cells. Front Mol Biosci 2021; 8:780033. [PMID: 34869600 PMCID: PMC8637157 DOI: 10.3389/fmolb.2021.780033] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Accepted: 10/14/2021] [Indexed: 11/24/2022] Open
Abstract
Extraction of membrane proteins from biological membranes has traditionally involved detergents. In the past decade, a new technique has been developed, which uses styrene maleic acid (SMA) copolymers to extract membrane proteins into nanodiscs without the requirement of detergents. SMA nanodiscs are compatible with analytical techniques, such as small-angle scattering, NMR spectroscopy, and DLS, and are therefore an attractive medium for membrane protein characterization. While mass spectrometry has also been reported as a technique compatible with copolymer extraction, most studies have focused on lipidomics, which involves solvent extraction of lipids from nanodiscs prior to mass-spectrometry analysis. In this study, mass spectrometry proteomics was used to investigate whether there are qualitative or quantitative differences in the mammalian plasma membrane proteins extracted with SMA compared to a detergent control. For this, cell surface proteins of 3T3L1 fibroblasts were biotinylated and extracted using either SMA or detergent. Following affinity pull-down of biotinylated proteins with NeutrAvidin beads, samples were analyzed by nanoLC-MS. Here, we report for the first time, a global proteomics protocol for detection of a mammalian cell "SMALPome", membrane proteins incorporated into SMA nanodiscs. Removal of SMA from samples prior to processing of samples for mass spectrometry was a crucial step in the protocol. The reported surface SMALPome of 3T3L1 fibroblasts consists of 205 integral membrane proteins. It is apparent that the detergent extraction method used is, in general, quantitatively more efficient at extracting proteins from the plasma membrane than SMA extraction. However, samples prepared following detergent extraction contained a greater proportion of proteins that were considered to be "non-specific" than in samples prepared from SMA extracts. Tantalizingly, it was also observed that proteins detected uniquely or highly preferentially in pull-downs from SMA extracts were primarily multi-spanning membrane proteins. These observations hint at qualitative differences between SMA and detergent extraction that are worthy of further investigation.
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Affiliation(s)
- Kerrie A. Morrison
- Department of Biology and Biochemistry, University of Bath, Bath, United Kingdom
- Department of Chemistry, University of Bath, Bath, United Kingdom
- Centre for Sustainable Circular Technologies, University of Bath, Bath, United Kingdom
| | - Kate J. Heesom
- University of Bristol, Proteomics Facility, Bristol, United Kingdom
| | - Karen J. Edler
- Department of Chemistry, University of Bath, Bath, United Kingdom
| | - James Doutch
- Rutherford Appleton Laboratory, ISIS Pulsed Neutron and Muon Source, Harwell Oxford, United Kingdom
| | - Gareth J. Price
- Department of Chemistry, University of Bath, Bath, United Kingdom
- Department of Chemistry, Khalifa University, Abu Dhabi, United Arab Emirates
| | | | - Paul Whitley
- Department of Biology and Biochemistry, University of Bath, Bath, United Kingdom
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37
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Biophysical characterisation of SMALPs. Biochem Soc Trans 2021; 49:2037-2050. [PMID: 34643233 DOI: 10.1042/bst20201088] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2021] [Revised: 09/22/2021] [Accepted: 09/23/2021] [Indexed: 11/17/2022]
Abstract
Membrane proteins such as receptors, ion channels and transport proteins are important drug targets. The structure-based study of membrane proteins is challenging, especially when the target protein contains both soluble and insoluble domains. Most membrane proteins are insoluble in aqueous solvent and embedded in the plasma membrane lipid bilayer, which significantly complicates biophysical studies. Poly(styrene-co-maleic acid) (SMA) and other polymer derivatives are increasingly common solubilisation agents, used to isolate membrane proteins stabilised in their native lipid environment in the total absence of detergent. Since the initial report of SMA-mediated solubilisation, and the formation of SMA lipid particles (SMALPs), this technique can directly isolate therapeutic targets from biological membranes, including G-protein coupled receptors (GPCRs). SMA now allows biophysical and structural analyses of membrane proteins in solution that was not previously possible. Here, we critically review several existing biophysical techniques compatible with SMALPs, with a focus on hydrodynamic analysis, microcalorimetric analysis and optical spectroscopic techniques.
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38
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Szundi I, Pitch SG, Chen E, Farrens DL, Kliger DS. Styrene-maleic acid copolymer effects on the function of the GPCR rhodopsin in lipid nanoparticles. Biophys J 2021; 120:4337-4348. [PMID: 34509506 DOI: 10.1016/j.bpj.2021.09.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2021] [Revised: 08/03/2021] [Accepted: 09/07/2021] [Indexed: 01/01/2023] Open
Abstract
Styrene-maleic acid (SMA) copolymers solubilize biological membranes to form lipid nanoparticles (SMALPs) that contain membrane proteins surrounded by native lipids, thus enabling the use of a variety of biophysical techniques for structural and functional studies. The question of whether SMALPs provide a truly natural environment or SMA solubilization affects the functional properties of membrane proteins, however, remains open. We address this question by comparing the photoactivation kinetics of rhodopsin, a G-protein-coupled receptor in the disk membranes of rod cells, in native membrane and SMALPs prepared at different molar ratios between SMA(3:1) and rhodopsin. Time-resolved absorption spectroscopy combined with complex kinetic analysis reveals kinetic and mechanistic differences between the native membrane and SMA-stabilized environment. The results suggest a range of molar ratios for nanoparticles suitable for kinetic studies.
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Affiliation(s)
- Istvan Szundi
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, Santa Cruz, California
| | - Stephanie G Pitch
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, Santa Cruz, California
| | - Eefei Chen
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, Santa Cruz, California
| | - David L Farrens
- Department of Chemical Physiology and Biochemistry, Oregon Health and Science University, Portland, Oregon
| | - David S Kliger
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, Santa Cruz, California.
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39
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Abstract
Membrane proteins (MPs) play essential roles in numerous cellular processes. Because around 70% of the currently marketed drugs target MPs, a detailed understanding of their structure, binding properties, and functional dynamics in a physiologically relevant environment is crucial for a more detailed understanding of this important protein class. We here summarize the benefits of using lipid nanodiscs for NMR structural investigations and provide a detailed overview of the currently used lipid nanodisc systems as well as their applications in solution-state NMR. Despite the increasing use of other structural methods for the structure determination of MPs in lipid nanodiscs, solution NMR turns out to be a versatile tool to probe a wide range of MP features, ranging from the structure determination of small to medium-sized MPs to probing ligand and partner protein binding as well as functionally relevant dynamical signatures in a lipid nanodisc setting. We will expand on these topics by discussing recent NMR studies with lipid nanodiscs and work out a key workflow for optimizing the nanodisc incorporation of an MP for subsequent NMR investigations. With this, we hope to provide a comprehensive background to enable an informed assessment of the applicability of lipid nanodiscs for NMR studies of a particular MP of interest.
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Affiliation(s)
- Umut Günsel
- Bavarian NMR Center (BNMRZ) at the Department of Chemistry, Technical University of Munich, Ernst-Otto-Fischer-Strasse 2, 85748 Garching, Germany
| | - Franz Hagn
- Bavarian NMR Center (BNMRZ) at the Department of Chemistry, Technical University of Munich, Ernst-Otto-Fischer-Strasse 2, 85748 Garching, Germany.,Institute of Structural Biology, Helmholtz Zentrum München, Ingolstädter Landstraße 1, 85764 Neuherberg, Germany
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40
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Majeed S, Ahmad AB, Sehar U, Georgieva ER. Lipid Membrane Mimetics in Functional and Structural Studies of Integral Membrane Proteins. MEMBRANES 2021; 11:685. [PMID: 34564502 PMCID: PMC8470526 DOI: 10.3390/membranes11090685] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Revised: 08/18/2021] [Accepted: 08/30/2021] [Indexed: 12/12/2022]
Abstract
Integral membrane proteins (IMPs) fulfill important physiological functions by providing cell-environment, cell-cell and virus-host communication; nutrients intake; export of toxic compounds out of cells; and more. However, some IMPs have obliterated functions due to polypeptide mutations, modifications in membrane properties and/or other environmental factors-resulting in damaged binding to ligands and the adoption of non-physiological conformations that prevent the protein from returning to its physiological state. Thus, elucidating IMPs' mechanisms of function and malfunction at the molecular level is important for enhancing our understanding of cell and organism physiology. This understanding also helps pharmaceutical developments for restoring or inhibiting protein activity. To this end, in vitro studies provide invaluable information about IMPs' structure and the relation between structural dynamics and function. Typically, these studies are conducted on transferred from native membranes to membrane-mimicking nano-platforms (membrane mimetics) purified IMPs. Here, we review the most widely used membrane mimetics in structural and functional studies of IMPs. These membrane mimetics are detergents, liposomes, bicelles, nanodiscs/Lipodisqs, amphipols, and lipidic cubic phases. We also discuss the protocols for IMPs reconstitution in membrane mimetics as well as the applicability of these membrane mimetic-IMP complexes in studies via a variety of biochemical, biophysical, and structural biology techniques.
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Affiliation(s)
- Saman Majeed
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409, USA
| | - Akram Bani Ahmad
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409, USA
| | - Ujala Sehar
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409, USA
| | - Elka R Georgieva
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409, USA
- Department of Cell Physiology and Molecular Biophysics, Texas Tech University Health Science Center, Lubbock, TX 79409, USA
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41
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Grime RL, Logan RT, Nestorow SA, Sridhar P, Edwards PC, Tate CG, Klumperman B, Dafforn TR, Poyner DR, Reeves PJ, Wheatley M. Differences in SMA-like polymer architecture dictate the conformational changes exhibited by the membrane protein rhodopsin encapsulated in lipid nano-particles. NANOSCALE 2021; 13:13519-13528. [PMID: 34477756 PMCID: PMC8359648 DOI: 10.1039/d1nr02419a] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Membrane proteins are of fundamental importance to cellular processes and nano-encapsulation strategies that preserve their native lipid bilayer environment are particularly attractive for studying and exploiting these proteins. Poly(styrene-co-maleic acid) (SMA) and related polymers poly(styrene-co-(N-(3-N',N'-dimethylaminopropyl)maleimide)) (SMI) and poly(diisobutylene-alt-maleic acid) (DIBMA) have revolutionised the study of membrane proteins by spontaneously solubilising membrane proteins direct from cell membranes within nanoscale discs of native bilayer called SMA lipid particles (SMALPs), SMILPs and DIBMALPs respectively. This systematic study shows for the first time, that conformational changes of the encapsulated protein are dictated by the solubilising polymer. The photoactivation pathway of rhodopsin (Rho), a G-protein-coupled receptor (GPCR), comprises structurally-defined intermediates with characteristic absorbance spectra that revealed conformational restrictions with styrene-containing SMA and SMI, so that photoactivation proceeded only as far as metarhodopsin-I, absorbing at 478 nm, in a SMALP or SMILP. In contrast, full attainment of metarhodopsin-II, absorbing at 382 nm, was observed in a DIBMALP. Consequently, different intermediate states of Rho could be generated readily by simply employing different SMA-like polymers. Dynamic light-scattering and analytical ultracentrifugation revealed differences in size and thermostability between SMALP, SMILP and DIBMALP. Moreover, encapsulated Rho exhibited different stability in a SMALP, SMILP or DIBMALP. Overall, we establish that SMA, SMI and DIBMA constitute a 'toolkit' of solubilising polymers, so that selection of the appropriate solubilising polymer provides a spectrum of useful attributes for studying membrane proteins.
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Affiliation(s)
- Rachael L Grime
- School of Biosciences, University of Birmingham, Birmingham, B15 2TT, UK
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42
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Hoffmann M, Haselberger D, Hofmann T, Müller L, Janson K, Meister A, Das M, Vargas C, Keller S, Kastritis PL, Schmidt C, Hinderberger D. Nanoscale Model System for the Human Myelin Sheath. Biomacromolecules 2021; 22:3901-3912. [PMID: 34324309 DOI: 10.1021/acs.biomac.1c00714] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Neurodegenerative disorders are among the most common diseases in modern society. However, the molecular bases of diseases such as multiple sclerosis or Charcot-Marie-Tooth disease remain far from being fully understood. Research in this field is limited by the complex nature of native myelin and by difficulties in obtaining good in vitro model systems of myelin. Here, we introduce an easy-to-use model system of the myelin sheath that can be used to study myelin proteins in a native-like yet well-controlled environment. To this end, we present myelin-mimicking nanodiscs prepared through one of the amphiphilic copolymers styrene/maleic acid (SMA), diisobutylene/maleic acid (DIBMA), and styrene/maleimide sulfobetaine (SMA-SB). These nanodiscs were tested for their lipid composition using chromatographic (HPLC) and mass spectrometric (MS) methods and, utilizing spin probes within the nanodisc, their comparability with liposomes was studied. In addition, their binding behavior with bovine myelin basic protein (MBP) was scrutinized to ensure that the nanodiscs represent a suitable model system of myelin. Our results suggest that both SMA and SMA-SB are able to solubilize the myelin-like (cytoplasmic) liposomes without preferences for specific lipid headgroups or fatty acyl chains. In nanodiscs of both SMA and SMA-SB (called SMA(-SB)-lipid particles, short SMALPs or SMA-SBLPs, respectively), the polymers restrict the lipids' motion in the hydrophobic center of the bilayer. The headgroups of the lipids, however, are sterically less hindered in nanodiscs when compared with liposomes. Myelin-like SMALPs are able to bind bovine MBP, which can stack the lipid bilayers like in native myelin, showing the usability of these simple, well-controlled systems in further studies of protein-lipid interactions of native myelin.
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Affiliation(s)
- Matthias Hoffmann
- Interdisciplinary Research Center HALOmem, Martin Luther University (MLU) Halle-Wittenberg, Charles Tanford Protein Center, Kurt-Mothes-Straße 3a, 06120 Halle (Saale), Germany.,Institute of Chemistry, Martin Luther University (MLU) Halle-Wittenberg, Von-Danckelmann-Platz 4, 06120 Halle (Saale), Germany
| | - David Haselberger
- Interdisciplinary Research Center HALOmem, Martin Luther University (MLU) Halle-Wittenberg, Charles Tanford Protein Center, Kurt-Mothes-Straße 3a, 06120 Halle (Saale), Germany.,Institute of Chemistry, Martin Luther University (MLU) Halle-Wittenberg, Von-Danckelmann-Platz 4, 06120 Halle (Saale), Germany
| | - Tommy Hofmann
- Interdisciplinary Research Center HALOmem, Martin Luther University (MLU) Halle-Wittenberg, Charles Tanford Protein Center, Kurt-Mothes-Straße 3a, 06120 Halle (Saale), Germany.,Institute of Biochemistry and Biotechnology, Martin Luther University (MLU) Halle-Wittenberg, Charles Tanford Protein Center, Kurt-Mothes-Straße 3a, 06120 Halle (Saale), Germany
| | - Lisa Müller
- Institute of Pharmacy, Martin Luther University (MLU) Halle-Wittenberg, Wolfgang-Langenbeck-Straße 4, 06120 Halle (Saale), Germany
| | - Kevin Janson
- Interdisciplinary Research Center HALOmem, Martin Luther University (MLU) Halle-Wittenberg, Charles Tanford Protein Center, Kurt-Mothes-Straße 3a, 06120 Halle (Saale), Germany.,Institute of Biochemistry and Biotechnology, Martin Luther University (MLU) Halle-Wittenberg, Charles Tanford Protein Center, Kurt-Mothes-Straße 3a, 06120 Halle (Saale), Germany
| | - Annette Meister
- Interdisciplinary Research Center HALOmem, Martin Luther University (MLU) Halle-Wittenberg, Charles Tanford Protein Center, Kurt-Mothes-Straße 3a, 06120 Halle (Saale), Germany.,Institute of Biochemistry and Biotechnology, Martin Luther University (MLU) Halle-Wittenberg, Charles Tanford Protein Center, Kurt-Mothes-Straße 3a, 06120 Halle (Saale), Germany
| | - Manabendra Das
- Molecular Biophysics, Technische Universität Kaiserslautern (TUK), Erwin-Schrödinger-Straße 13, 67663 Kaiserslautern, Germany
| | - Carolyn Vargas
- Molecular Biophysics, Technische Universität Kaiserslautern (TUK), Erwin-Schrödinger-Straße 13, 67663 Kaiserslautern, Germany.,Biophysics, Institute of Molecular Biosciences (IMB), NAWI Graz, University of Graz, Humboldtstraße 50/III, 8010 Graz, Austria.,Field of Excellence BioHealth, University of Graz, 8010 Graz, Austria.,BioTechMed-Graz, 8010 Graz, Austria
| | - Sandro Keller
- Molecular Biophysics, Technische Universität Kaiserslautern (TUK), Erwin-Schrödinger-Straße 13, 67663 Kaiserslautern, Germany.,Biophysics, Institute of Molecular Biosciences (IMB), NAWI Graz, University of Graz, Humboldtstraße 50/III, 8010 Graz, Austria.,Field of Excellence BioHealth, University of Graz, 8010 Graz, Austria.,BioTechMed-Graz, 8010 Graz, Austria
| | - Panagiotis L Kastritis
- Interdisciplinary Research Center HALOmem, Martin Luther University (MLU) Halle-Wittenberg, Charles Tanford Protein Center, Kurt-Mothes-Straße 3a, 06120 Halle (Saale), Germany.,Institute of Biochemistry and Biotechnology, Martin Luther University (MLU) Halle-Wittenberg, Charles Tanford Protein Center, Kurt-Mothes-Straße 3a, 06120 Halle (Saale), Germany
| | - Carla Schmidt
- Interdisciplinary Research Center HALOmem, Martin Luther University (MLU) Halle-Wittenberg, Charles Tanford Protein Center, Kurt-Mothes-Straße 3a, 06120 Halle (Saale), Germany.,Institute of Biochemistry and Biotechnology, Martin Luther University (MLU) Halle-Wittenberg, Charles Tanford Protein Center, Kurt-Mothes-Straße 3a, 06120 Halle (Saale), Germany
| | - Dariush Hinderberger
- Interdisciplinary Research Center HALOmem, Martin Luther University (MLU) Halle-Wittenberg, Charles Tanford Protein Center, Kurt-Mothes-Straße 3a, 06120 Halle (Saale), Germany.,Institute of Chemistry, Martin Luther University (MLU) Halle-Wittenberg, Von-Danckelmann-Platz 4, 06120 Halle (Saale), Germany
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43
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Biological insights from SMA-extracted proteins. Biochem Soc Trans 2021; 49:1349-1359. [PMID: 34110372 PMCID: PMC8286838 DOI: 10.1042/bst20201067] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2021] [Revised: 05/12/2021] [Accepted: 05/17/2021] [Indexed: 02/08/2023]
Abstract
In the twelve years since styrene maleic acid (SMA) was first used to extract and purify a membrane protein within a native lipid bilayer, this technological breakthrough has provided insight into the structural and functional details of protein–lipid interactions. Most recently, advances in cryo-EM have demonstrated that SMA-extracted membrane proteins are a rich-source of structural data. For example, it has been possible to resolve the details of annular lipids and protein–protein interactions within complexes, the nature of lipids within central cavities and binding pockets, regions involved in stabilising multimers, details of terminal residues that would otherwise remain unresolved and the identification of physiologically relevant states. Functionally, SMA extraction has allowed the analysis of membrane proteins that are unstable in detergents, the characterization of an ultrafast component in the kinetics of electron transfer that was not possible in detergent-solubilised samples and quantitative, real-time measurement of binding assays with low concentrations of purified protein. While the use of SMA comes with limitations such as its sensitivity to low pH and divalent cations, its major advantage is maintenance of a protein's lipid bilayer. This has enabled researchers to view and assay proteins in an environment close to their native ones, leading to new structural and mechanistic insights.
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44
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Brady NG, Workman CE, Cawthon B, Bruce BD, Long BK. Protein Extraction Efficiency and Selectivity of Esterified Styrene-Maleic Acid Copolymers in Thylakoid Membranes. Biomacromolecules 2021; 22:2544-2553. [PMID: 34038122 DOI: 10.1021/acs.biomac.1c00274] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Amphiphilic styrene-maleic acid copolymers (SMAs) have been shown to effectively extract membrane proteins surrounded by an annulus of native membrane lipids via the formation of nanodiscs. Recent reports have shown that 2-butoxyethanol-functionalized SMA derivatives promote the extraction of membrane proteins from thylakoid membranes, whereas unfunctionalized SMA is essentially ineffective. However, it is unknown how the extent of functionalization and identity of sidechains impact protein solubilization and specificity. Herein, we show that the monoesterification of an SMA polymer with hydrophobic alkoxy ethoxylate sidechains leads to an increased solubilization efficiency (SE) of trimeric photosystem I (PSI) from the membranes of cyanobacterium Thermosynechococcus elongatus. The specific SMA polymer used in this study, PRO 10235, cannot encapsulate single PSI trimers from this cyanobacterium; however, as it is functionalized with alkoxy ethoxylates of increasing alkoxy chain length, a clear increase in the trimeric PSI SE is observed. Furthermore, an exponential increase in the SE is observed when >50% of the maleic acid repeat units are monoesterified with long alkoxy ethoxylates, suggesting that the PSI extraction mechanism is highly dependent on both the number and length of the attached side chains.
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Affiliation(s)
- Nathan G Brady
- Department of Biochemistry & Cellular and Molecular Biology, University of Tennessee, Knoxville 37996-1939, Tennessee, United States
| | - Cameron E Workman
- Department of Chemistry, University of Tennessee, Knoxville 37996-1600, Tennessee, United States
| | - Bridgie Cawthon
- Department of Chemical and Biomolecular Engineering, University of Tennessee, Knoxville 37996-0840, Tennessee, United States
| | - Barry D Bruce
- Department of Biochemistry & Cellular and Molecular Biology, University of Tennessee, Knoxville 37996-1939, Tennessee, United States.,Department of Chemical and Biomolecular Engineering, University of Tennessee, Knoxville 37996-0840, Tennessee, United States
| | - Brian K Long
- Department of Chemistry, University of Tennessee, Knoxville 37996-1600, Tennessee, United States
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45
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Bjørnestad V, Orwick-Rydmark M, Lund R. Understanding the Structural Pathways for Lipid Nanodisc Formation: How Styrene Maleic Acid Copolymers Induce Membrane Fracture and Disc Formation. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:6178-6188. [PMID: 33979520 PMCID: PMC8280715 DOI: 10.1021/acs.langmuir.1c00304] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/03/2021] [Revised: 04/28/2021] [Indexed: 06/12/2023]
Abstract
Lipid nanodiscs formed by mixtures of styrene maleic acid (SMA) copolymers and lipid membranes are important tools for studying membrane proteins in many biotechnological applications. However, molecular interactions leading up to their formation are not well understood. Here, we elucidate the nanodisc formation pathways for SMA/lipid vesicle mixtures using small-angle X-ray scattering (SAXS) that allows detailed in situ nanostructural information. SMA copolymer that is initially aggregated in solution inserts its styrene units into the lipid bilayer hydrocarbon region, leading to fractures in the membrane. The initial copolymer-lipid interactions observed in the vesicles are also present in the formed discs, with excess copolymer distributed along the normal of the bilayer. The size and SMA distribution in the resulting discs strongly depend on the temperature, lipid/copolymer ratio, and lipid type. We find that the solubilization limit increases for membranes above the melting point, suggesting that defects in gel-like lipid membranes play a significant role in membrane fracturing and nanodisc formation. These findings provide unique insights into the formation of nanodiscs as well as into the microscopic mechanism of solubilization, which plays an important role in many applications and products ranging from household goods to biotechnology and medicine.
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Affiliation(s)
| | | | - Reidar Lund
- Department
of Chemistry, University of Oslo, Sem Sælandsvei 26, 0371 Oslo, Norway
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46
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Pitch SG, Yao W, Szundi I, Fay J, Chen E, Shumate A, Kliger DS, Farrens DL. Functional integrity of membrane protein rhodopsin solubilized by styrene-maleic acid copolymer. Biophys J 2021; 120:3508-3515. [PMID: 34022241 DOI: 10.1016/j.bpj.2021.05.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2020] [Revised: 04/18/2021] [Accepted: 05/13/2021] [Indexed: 11/25/2022] Open
Abstract
Membrane proteins often require solubilization to study their structure or define the mechanisms underlying their function. In this study, the functional properties of the membrane protein rhodopsin in its native lipid environment were investigated after being solubilized with styrene-maleic acid (SMA) copolymer. The static absorption spectra of rhodopsin before and after the addition of SMA were recorded at room temperature to quantify the amount of membrane protein solubilized. The samples were then photobleached to analyze the functionality of rhodopsin upon solubilization. Samples with low or high SMA/rhodopsin ratios were compared to find a threshold in which the maximal amount of active rhodopsin was solubilized from membrane suspensions. Interestingly, whereas the highest SMA/rhodopsin ratios yielded the most solubilized rhodopsin, the rhodopsin produced under these conditions could not reach the active (Meta II) state upon photoactivation. The results confirm that SMA is a useful tool for membrane protein research, but SMA added in excess can interfere with the dynamics of protein activation.
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Affiliation(s)
- Stephanie G Pitch
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, Santa Cruz, California
| | - Weekie Yao
- Department of Chemical Physiology and Biochemistry, Oregon Health and Science University, Portland, Oregon
| | - Istvan Szundi
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, Santa Cruz, California
| | - Jonathan Fay
- Department of Chemical Physiology and Biochemistry, Oregon Health and Science University, Portland, Oregon
| | - Eefei Chen
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, Santa Cruz, California
| | - Anthony Shumate
- Department of Chemical Physiology and Biochemistry, Oregon Health and Science University, Portland, Oregon
| | - David S Kliger
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, Santa Cruz, California
| | - David L Farrens
- Department of Chemical Physiology and Biochemistry, Oregon Health and Science University, Portland, Oregon.
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47
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Zhang S, Go EP, Ding H, Anang S, Kappes JC, Desaire H, Sodroski J. Analysis of glycosylation and disulfide bonding of wild-type SARS-CoV-2 spike glycoprotein. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2021. [PMID: 33821278 PMCID: PMC8020978 DOI: 10.1101/2021.04.01.438120] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The SARS-CoV-2 coronavirus, the etiologic agent of COVID-19, uses its spike (S) glycoprotein anchored in the viral membrane to enter host cells. The S glycoprotein is the major target for neutralizing antibodies elicited by natural infection and by vaccines. Approximately 35% of the SARS-CoV-2 S glycoprotein consists of carbohydrate, which can influence virus infectivity and susceptibility to antibody inhibition. We found that virus-like particles produced by coexpression of SARS-CoV-2 S, M, E and N proteins contained spike glycoproteins that were extensively modified by complex carbohydrates. We used a fucose-selective lectin to enrich the Golgi-resident fraction of a wild-type SARS-CoV-2 S glycoprotein trimer, and determined its glycosylation and disulfide bond profile. Compared with soluble or solubilized S glycoproteins modified to prevent proteolytic cleavage and to retain a prefusion conformation, more of the wild-type S glycoprotein N-linked glycans are processed to complex forms. Even Asn 234, a significant percentage of which is decorated by high-mannose glycans on soluble and virion S trimers, is predominantly modified in the Golgi by processed glycans. Three incompletely occupied sites of O-linked glycosylation were detected. Viruses pseudotyped with natural variants of the serine/threonine residues implicated in O-linked glycosylation were generally infectious and exhibited sensitivity to neutralization by soluble ACE2 and convalescent antisera comparable to that of the wild-type virus. Unlike other natural cysteine variants, a Cys15Phe (C15F) mutant retained partial, but unstable, infectivity. These findings enhance our understanding of the Golgi processing of the native SARS-CoV-2 S glycoprotein carbohydrates and could assist the design of interventions.
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48
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Probing Structural Dynamics of Membrane Proteins Using Electron Paramagnetic Resonance Spectroscopic Techniques. BIOPHYSICA 2021. [DOI: 10.3390/biophysica1020009] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Membrane proteins are essential for the survival of living organisms. They are involved in important biological functions including transportation of ions and molecules across the cell membrane and triggering the signaling pathways. They are targets of more than half of the modern medical drugs. Despite their biological significance, information about the structural dynamics of membrane proteins is lagging when compared to that of globular proteins. The major challenges with these systems are low expression yields and lack of appropriate solubilizing medium required for biophysical techniques. Electron paramagnetic resonance (EPR) spectroscopy coupled with site directed spin labeling (SDSL) is a rapidly growing powerful biophysical technique that can be used to obtain pertinent structural and dynamic information on membrane proteins. In this brief review, we will focus on the overview of the widely used EPR approaches and their emerging applications to answer structural and conformational dynamics related questions on important membrane protein systems.
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49
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Lipidomic and in-gel analysis of maleic acid co-polymer nanodiscs reveals differences in composition of solubilized membranes. Commun Biol 2021; 4:218. [PMID: 33594255 PMCID: PMC7886889 DOI: 10.1038/s42003-021-01711-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Accepted: 01/12/2021] [Indexed: 01/30/2023] Open
Abstract
Membrane proteins are key in a large number of physiological and pathological processes. Their study often involves a prior detergent solubilization step, which strips away the membrane and can jeopardize membrane protein integrity. A recent alternative to detergents encompasses maleic acid based copolymers (xMAs), which disrupt the lipid bilayer and form lipid protein nanodiscs (xMALPs) soluble in aqueous buffer. Although xMALPs are often referred to as native nanodiscs, little is known about the resemblance of their lipid and protein content to the native bilayer. Here we have analyzed prokaryotic and eukaryotic xMALPs using lipidomics and in-gel analysis. Our results show that the xMALPs content varies with the chemical properties of the used xMA.
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50
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Olerinyova A, Sonn-Segev A, Gault J, Eichmann C, Schimpf J, Kopf AH, Rudden LSP, Ashkinadze D, Bomba R, Frey L, Greenwald J, Degiacomi MT, Steinhilper R, Killian JA, Friedrich T, Riek R, Struwe WB, Kukura P. Mass Photometry of Membrane Proteins. Chem 2021; 7:224-236. [PMID: 33511302 PMCID: PMC7815066 DOI: 10.1016/j.chempr.2020.11.011] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Revised: 08/20/2020] [Accepted: 11/11/2020] [Indexed: 02/07/2023]
Abstract
Integral membrane proteins (IMPs) are biologically highly significant but challenging to study because they require maintaining a cellular lipid-like environment. Here, we explore the application of mass photometry (MP) to IMPs and membrane-mimetic systems at the single-particle level. We apply MP to amphipathic vehicles, such as detergents and amphipols, as well as to lipid and native nanodiscs, characterizing the particle size, sample purity, and heterogeneity. Using methods established for cryogenic electron microscopy, we eliminate detergent background, enabling high-resolution studies of membrane-protein structure and interactions. We find evidence that, when extracted from native membranes using native styrene-maleic acid nanodiscs, the potassium channel KcsA is present as a dimer of tetramers—in contrast to results obtained using detergent purification. Finally, using lipid nanodiscs, we show that MP can help distinguish between functional and non-functional nanodisc assemblies, as well as determine the critical factors for lipid nanodisc formation. We introduce a label-free, single molecule approach for membrane-protein characterization Mass photometry quantifies membrane proteins in different membrane-mimetic systems MP reveals carrier and protein heterogeneity It helps distinguish different functional states of membrane proteins
Membrane proteins are some of the most important biological molecules, carrying out vital functions and being frequent drug targets. Yet, preferring lipid environments and so requiring solubilization, they are challenging to study. Here, we show that mass photometry can characterize the heterogeneity of membrane proteins and the carriers in which they are solubilized. It can also distinguish different functional states of membrane proteins. Our approach thus opens the door to more comprehensive studies of function, structure, and interaction of these critical proteins in their native membrane environment at the single-molecule level.
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Affiliation(s)
- Anna Olerinyova
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QZ, UK
| | - Adar Sonn-Segev
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QZ, UK
| | - Joseph Gault
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QZ, UK
| | - Cédric Eichmann
- Laboratory of Physical Chemistry, Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 1-5/10, 8093 Zürich, Switzerland
| | - Johannes Schimpf
- Institut für Biochemie, Albert-Ludwigs-Universität, Alberstraße 21, 79104 Freiburg im Breisgau, Germany
| | - Adrian H Kopf
- Membrane Biochemistry & Biophysics, Bijvoet Center for Biomolecular Research, Department of Chemistry, Utrecht University, Padualaan 8, Utrecht 3584 CH, the Netherlands
| | - Lucas S P Rudden
- Department of Physics, Durham University, Lower Mountjoy, South Road, Durham DH1 3LE, UK
| | - Dzmitry Ashkinadze
- Laboratory of Physical Chemistry, Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 1-5/10, 8093 Zürich, Switzerland
| | - Radoslaw Bomba
- Laboratory of Physical Chemistry, Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 1-5/10, 8093 Zürich, Switzerland
| | - Lukas Frey
- Laboratory of Physical Chemistry, Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 1-5/10, 8093 Zürich, Switzerland
| | - Jason Greenwald
- Laboratory of Physical Chemistry, Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 1-5/10, 8093 Zürich, Switzerland
| | - Matteo T Degiacomi
- Department of Physics, Durham University, Lower Mountjoy, South Road, Durham DH1 3LE, UK
| | - Ralf Steinhilper
- Laboratory of Physical Chemistry, Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 1-5/10, 8093 Zürich, Switzerland
| | - J Antoinette Killian
- Membrane Biochemistry & Biophysics, Bijvoet Center for Biomolecular Research, Department of Chemistry, Utrecht University, Padualaan 8, Utrecht 3584 CH, the Netherlands
| | - Thorsten Friedrich
- Institut für Biochemie, Albert-Ludwigs-Universität, Alberstraße 21, 79104 Freiburg im Breisgau, Germany
| | - Roland Riek
- Laboratory of Physical Chemistry, Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 1-5/10, 8093 Zürich, Switzerland
| | - Weston B Struwe
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QZ, UK
| | - Philipp Kukura
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QZ, UK
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