1
|
Galvagnion C, Barclay A, Makasewicz K, Marlet FR, Moulin M, Devos JM, Linse S, Martel A, Porcar L, Sparr E, Pedersen MC, Roosen-Runge F, Arleth L, Buell AK. Structural characterisation of α-synuclein-membrane interactions and the resulting aggregation using small angle scattering. Phys Chem Chem Phys 2024; 26:10998-11013. [PMID: 38526443 DOI: 10.1039/d3cp05928f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/26/2024]
Abstract
The presence of amyloid fibrils is a hallmark of several neurodegenerative diseases. Some amyloidogenic proteins, such as α-synuclein and amyloid β, interact with lipids, and this interaction can strongly favour the formation of amyloid fibrils. In particular the primary nucleation step, i.e. the de novo formation of amyloid fibrils, has been shown to be accelerated by lipids. However, the exact mechanism of this acceleration is still mostly unclear. Here we use a range of scattering methods, such as dynamic light scattering (DLS) and small angle X-ray and neutron scattering (SAXS and SANS) to obtain structural information on the binding of α-synuclein to model membranes formed from negatively charged lipids and their co-assembly into amyloid fibrils. We find that the model membranes take an active role in the reaction. The binding of α synuclein to the model membranes immediately induces a major structural change in the lipid assembly, which leads to a break-up into small and mostly disc- or rod-like lipid-protein particles. This transition can be reversed by temperature changes or proteolytic protein removal. Incubation of the small lipid-α-synuclein particles for several hours, however, leads to amyloid fibril formation, whereby the lipids are incorporated into the amyloid fibrils.
Collapse
Affiliation(s)
- Céline Galvagnion
- Department of Drug Design and Pharmacology, University of Copenhagen, 2100 Copenhagen, Denmark.
| | - Abigail Barclay
- Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Katarzyna Makasewicz
- Division of Physical Chemistry, Center for Chemistry and Chemical Engineering, Lund University, P.O. Box 124, SE-22100, Lund, Sweden
| | | | - Martine Moulin
- Institut Laue-Langevin, 71 avenue des Martyrs, 38042 Grenoble, France
| | - Juliette M Devos
- Institut Laue-Langevin, 71 avenue des Martyrs, 38042 Grenoble, France
| | - Sara Linse
- Department of Biochemistry and Structural Biology, Lund University, SE22100 Lund, Sweden
| | - Anne Martel
- Institut Laue-Langevin, 71 avenue des Martyrs, 38042 Grenoble, France
| | - Lionel Porcar
- Institut Laue-Langevin, 71 avenue des Martyrs, 38042 Grenoble, France
| | - Emma Sparr
- Division of Physical Chemistry, Center for Chemistry and Chemical Engineering, Lund University, P.O. Box 124, SE-22100, Lund, Sweden
| | | | - Felix Roosen-Runge
- Division of Physical Chemistry, Center for Chemistry and Chemical Engineering, Lund University, P.O. Box 124, SE-22100, Lund, Sweden
- Department of Biomedical Sciences and Biofilms Research Center for Biointerfaces, Malmö University, Malmö, Sweden
| | - Lise Arleth
- Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Alexander K Buell
- Department of Biotechnology and Biomedicine, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark.
| |
Collapse
|
2
|
Ruan M, Li H, Zhang Y, Zhao R, Zhang J, Wang Y, Gao J, Wang Z, Wang Y, Sun D, Ding W, Weng Y. Cryo-EM structures of LHCII in photo-active and photo-protecting states reveal allosteric regulation of light harvesting and excess energy dissipation. Nat Plants 2023; 9:1547-1557. [PMID: 37653340 DOI: 10.1038/s41477-023-01500-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2023] [Accepted: 07/26/2023] [Indexed: 09/02/2023]
Abstract
The major light-harvesting complex of photosystem II (LHCII) has a dual regulatory function in a process called non-photochemical quenching to avoid the formation of reactive oxygen. LHCII undergoes reversible conformation transitions to switch between a light-harvesting state for excited-state energy transfer and an energy-quenching state for dissipating excess energy under full sunshine. Here we report cryo-electron microscopy structures of LHCII in membrane nanodiscs, which mimic in vivo LHCII, and in detergent solution at pH 7.8 and 5.4, respectively. We found that, under low pH conditions, the salt bridges at the lumenal side of LHCII are broken, accompanied by the formation of two local α-helices on the lumen side. The formation of α-helices in turn triggers allosterically global protein conformational change, resulting in a smaller crossing angle between transmembrane helices. The fluorescence decay rates corresponding to different conformational states follow the Dexter energy transfer mechanism with a characteristic transition distance of 5.6 Å between Lut1 and Chl612. The experimental observations are consistent with the computed electronic coupling strengths using multistate density function theory.
Collapse
Affiliation(s)
- Meixia Ruan
- Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Hao Li
- School of Chemical Biology and Biotechnology, Peking University Shenzhen Graduate School, Shenzhen, China
- Institute of Systems and Physical Biology, Shenzhen Bay Laboratory, Shenzhen, China
| | - Ying Zhang
- Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Ruoqi Zhao
- Institute of Systems and Physical Biology, Shenzhen Bay Laboratory, Shenzhen, China
| | - Jun Zhang
- Institute of Systems and Physical Biology, Shenzhen Bay Laboratory, Shenzhen, China
| | - Yingjie Wang
- Institute of Systems and Physical Biology, Shenzhen Bay Laboratory, Shenzhen, China
| | - Jiali Gao
- School of Chemical Biology and Biotechnology, Peking University Shenzhen Graduate School, Shenzhen, China.
- Institute of Systems and Physical Biology, Shenzhen Bay Laboratory, Shenzhen, China.
- Department of Chemistry and Supercomputing Institute, University of Minnesota, Minneapolis, MN, USA.
| | - Zhuan Wang
- Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China
| | - Yumei Wang
- Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China
| | - Dapeng Sun
- Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China
| | - Wei Ding
- Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China.
- University of Chinese Academy of Sciences, Beijing, China.
| | - Yuxiang Weng
- Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China.
- University of Chinese Academy of Sciences, Beijing, China.
- Songshan Lake Materials Laboratory, Dongguan, China.
| |
Collapse
|
3
|
Barclay A, Kragelund BB, Arleth L, Pedersen MC. Modeling of flexible membrane-bound biomolecular complexes for solution small-angle scattering. J Colloid Interface Sci 2023; 635:611-621. [PMID: 36634513 DOI: 10.1016/j.jcis.2022.12.024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2022] [Revised: 11/18/2022] [Accepted: 12/06/2022] [Indexed: 12/14/2022]
Abstract
Recent advances in protein expression protocols, sample handling, and experimental set up of small-angle scattering experiments have allowed users of the technique to structurally investigate biomolecules of growing complexity and structural disorder. Notable examples include intrinsically disordered proteins, multi-domain proteins and membrane proteins in suitable carrier systems. Here, we outline a modeling scheme for calculating the scattering profiles from such complex samples. This kind of modeling is necessary for structural information to be refined from the corresponding data. The scheme bases itself on a hybrid of classical form factor based modeling and the well-known spherical harmonics-based formulation of small-angle scattering amplitudes. Our framework can account for flexible domains alongside other structurally elaborate components of the molecular system in question. We demonstrate the utility of this modeling scheme through a recent example of a structural model of the growth hormone receptor membrane protein in a phospholipid bilayer nanodisc which is refined against experimental SAXS data. Additionally we investigate how the scattering profiles from the complex would appear under different scattering contrasts. For each contrast situation we discuss what structural information is contained and the related consequences for modeling of the data.
Collapse
Affiliation(s)
- Abigail Barclay
- Condensed Matter Physics, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, Copenhagen 2100, Denmark.
| | - Birthe B Kragelund
- Structural Biology and NMR Laboratory, Department of Biology, University of Copenhagen, Ole Maaløes Vej 5, Copenhagen 2200, Denmark.
| | - Lise Arleth
- Condensed Matter Physics, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, Copenhagen 2100, Denmark.
| | - Martin Cramer Pedersen
- Condensed Matter Physics, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, Copenhagen 2100, Denmark.
| |
Collapse
|
4
|
Lenz J, Larsen AH, Keller S, Luchini A. Effect of Cholesterol on the Structure and Composition of Glyco-DIBMA Lipid Particles. Langmuir 2023; 39:3569-3579. [PMID: 36854196 PMCID: PMC10018766 DOI: 10.1021/acs.langmuir.2c03019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/04/2022] [Revised: 02/16/2023] [Indexed: 06/18/2023]
Abstract
Different amphiphilic co-polymers have been introduced to produce polymer-lipid particles with nanodisc structure composed of an inner lipid bilayer and polymer chains self-assembled as an outer belt. These particles can be used to stabilize membrane proteins in solution and enable their characterization by means of biophysical methods, including small-angle X-ray scattering (SAXS). Some of these co-polymers have also been used to directly extract membrane proteins together with their associated lipids from native membranes. Styrene/maleic acid and diisobutylene/maleic acid are among the most commonly used co-polymers for producing polymer-lipid particles, named SMALPs and DIBMALPs, respectively. Recently, a new co-polymer, named Glyco-DIBMA, was produced by partial amidation of DIBMA with the amino sugar N-methyl-d-glucosamine. Polymer-lipid particles produced with Glyco-DIBMA, named Glyco-DIBMALPs, exhibit improved structural properties and stability compared to those of SMALPs and DIBMALPs while retaining the capability of directly extracting membrane proteins from native membranes. Here, we characterize the structure and lipid composition of Glyco-DIBMALPs produced with either 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) or 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC). Glyco-DIBMALPs were also prepared with mixtures of either POPC or DMPC and cholesterol at different mole fractions. We estimated the lipid content in the Glyco-DIBMALPs and determined the particle structure and morphology by SAXS. We show that the Glyco-DIBMALPs are nanodisc-like particles whose size and shape depend on the polymer/lipid ratio. This is relevant for designing nanodisc particles with a tunable diameter according to the size of the membrane protein to be incorporated. We also report that the addition of >20 mol % cholesterol strongly perturbed the formation of Glyco-DIBMALPs. Altogether, we describe a detailed characterization of the Glyco-DIBMALPs, which provides relevant inputs for future application of these particles in the biophysical investigation of membrane proteins.
Collapse
Affiliation(s)
- Julia Lenz
- Molecular
Biophysics, Technische Universität
Kaiserslautern, Erwin-Schrödinger-Strasse
13, 67663 Kaiserslautern, Germany
| | | | - Sandro Keller
- 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
| | - Alessandra Luchini
- European
Spallation Source - ERIC, Partikel Gatan, Lund 224
84, Sweden
- Department
of Physics and Geology, University of Perugia, Via Alessandro Pascoli, 06123 Perugia, Italy
| |
Collapse
|
5
|
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] [What about the content of this article? (0)] [Affiliation(s)] [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.
Collapse
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
| |
Collapse
|
6
|
Martin J, Robert X, Gouet P, Falson P, Chaptal V. Specific Xray diffraction patterns of membrane proteins caused by secondary structure collinearity. Biochim Biophys Acta Biomembr 2023; 1865:184065. [PMID: 36206830 DOI: 10.1016/j.bbamem.2022.184065] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2022] [Revised: 09/12/2022] [Accepted: 09/30/2022] [Indexed: 11/07/2022]
Abstract
Diffraction anisotropy is a phenomenon that impacts more specifically membrane proteins, compared to soluble ones, but the reasons for this discrepancy remained unclear. Often, it is referred to a difference in resolution limits between highest and lowest diffraction limits as a signature for anisotropy. We show in this article that there is no single correlation between anisotropy and difference in resolution limits, with notably a substantial number of structures displaying various anisotropy with no difference in resolution limits. We further investigated diffraction intensity profiles, and observed a peak centred on 4.9 Å resolution more predominant in membrane proteins. Since this peak is in the region corresponding to secondary structures, we investigated the influence of secondary structure ratio. We showed that secondary structure content has little influence on this profile, while secondary structure collinearity in membrane proteins correlate with a stronger peak. Finally, we could further show that the presence of this peak is linked to higher diffraction anisotropy. These results bring to light a specific diffraction of membrane protein crystals, which calls for a specific handling by crystallographic software. It also brings an explanation for investigators struggling with their anisotropic data.
Collapse
Affiliation(s)
- Juliette Martin
- Molecular Microbiology and Structural Biochemistry Laboratory, CNRS UMR 5086, University of Lyon, IBCP, 7, passage du Vercors, 69367 Lyon, France
| | - Xavier Robert
- Molecular Microbiology and Structural Biochemistry Laboratory, CNRS UMR 5086, University of Lyon, IBCP, 7, passage du Vercors, 69367 Lyon, France
| | - Patrice Gouet
- Molecular Microbiology and Structural Biochemistry Laboratory, CNRS UMR 5086, University of Lyon, IBCP, 7, passage du Vercors, 69367 Lyon, France
| | - Pierre Falson
- Molecular Microbiology and Structural Biochemistry Laboratory, CNRS UMR 5086, University of Lyon, IBCP, 7, passage du Vercors, 69367 Lyon, France
| | - Vincent Chaptal
- Molecular Microbiology and Structural Biochemistry Laboratory, CNRS UMR 5086, University of Lyon, IBCP, 7, passage du Vercors, 69367 Lyon, France.
| |
Collapse
|
7
|
Ho PS, Kao TY, Li CC, Lan YJ, Lai YC, Chiang YW. Nanodisc Lipids Exhibit Singular Behaviors Implying Critical Phenomena. Langmuir 2022; 38:15372-15383. [PMID: 36454955 DOI: 10.1021/acs.langmuir.2c02596] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Nanodiscs are broadly used for characterization of membrane proteins as they are generally assumed to provide a near-native environment. In fact, it is an open question whether the physical properties of lipids in nanodiscs and membrane vesicles of the same lipid composition are identical. Here, we investigate the properties of lipids (1,2-dipalmitoyl-sn-glycero-3-phosphocholine, 1,2-dilauroyl-sn-glycero-3-phosphocholine, and their mixtures) in two different sample types, nanodiscs and multilamellar vesicles, by means of spin-label electron spin resonance techniques. Our results provide a quantitative description of lipid dynamics and ordering, elucidating the molecular details of how lipids in the two sample types behave differently in response to temperature and lipid composition. We show that the properties of lipids are altered in nanodiscs such that the dissimilarity of the fluid and gel lipid phases is reduced, and the first-order phase transitions are largely abolished in nanodiscs. We unveil that the ensemble of lipids in the middle of a nanodisc bilayer, as probed by the end-chain spin-label 16-PC, is promoted to a state close to a miscibility critical point, thereby rendering the phase transitions continuous. Critical phenomena have recently been proposed to explain features of the heterogeneity in native cell membranes. Our results lay the groundwork for how to establish a near-native environment in nanodiscs with simple organization of lipid components.
Collapse
Affiliation(s)
- Pei-Shan Ho
- Department of Chemistry, National Tsing Hua University, Hsinchu 300-044, Taiwan
| | - Te-Yu Kao
- Department of Chemistry, National Tsing Hua University, Hsinchu 300-044, Taiwan
| | - Chieh-Chin Li
- Department of Chemistry, National Tsing Hua University, Hsinchu 300-044, Taiwan
| | - Yu-Jing Lan
- Department of Chemistry, National Tsing Hua University, Hsinchu 300-044, Taiwan
| | - Yei-Chen Lai
- Department of Chemistry, National Chung Hsing University, Taichung 402-002, Taiwan
| | - Yun-Wei Chiang
- Department of Chemistry, National Tsing Hua University, Hsinchu 300-044, Taiwan
| |
Collapse
|
8
|
Tidemand FG, Blemmer S, Johansen NT, Arleth L, Pedersen MC. Non-ionic detergent assists formation of supercharged nanodiscs and insertion of membrane proteins. Biochim Biophys Acta Biomembr 2022; 1864:183884. [PMID: 35182589 DOI: 10.1016/j.bbamem.2022.183884] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2021] [Revised: 01/18/2022] [Accepted: 02/01/2022] [Indexed: 12/12/2022]
Abstract
Nanodiscs are used to stabilize membrane proteins in a lipid environment and enable investigations of the function and structure of these. Membrane proteins are often only available in small amounts, and thus the stability and ease of use of the nanodiscs are essential. We have recently explored circularizing and supercharging membrane scaffolding proteins (MSPs) for nanodisc formation and found increased temporal stability at elevated temperatures. In the present study, we investigate six different supercharged MSPs and their ability to form nanodiscs: three covalently circularized and the three non-circularized, linear versions. Using standard reconstitution protocols using cholate as the reconstitution detergent, we found that two of the linear constructs formed multiple lipid-protein species, whereas adding n-Dodecyl-B-D-maltoside (DDM) with the cholate in the reconstitution gave rise to single-species nanodisc formation for these MSPs. For all MSPs, the formed nanodiscs were analyzed by small-angle X-ray scattering (SAXS), which showed similar structures for each MSP, respectively, suggesting that the structures of the formed nanodiscs are independent of the initial DDM content, as long as cholate is present. Lastly, we incorporated the membrane protein proteorhodopsin into the supercharged nanodiscs and observed a considerable increase in incorporation yield with the addition of DDM. For the three circularized MSPs, a single major species appeared in the size exclusion chromatography (SEC) chromatogram, suggesting monodisperse nanodiscs with proteorhodopsin incorporated, which is in strong contrast to the samples without DDM showing almost no incorporation and high polydispersity.
Collapse
Affiliation(s)
- Frederik G Tidemand
- Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
| | - Sara Blemmer
- Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
| | - Nicolai T Johansen
- Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark; Section for Transport Biology, Department of Plant and Environmental Sciences, University of Copenhagen, 1871 Frederiksberg C, Denmark
| | - Lise Arleth
- Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
| | - Martin Cramer Pedersen
- Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark.
| |
Collapse
|
9
|
Barclay A, Tidemand Johansen N, Tidemand FG, Arleth L, Pedersen MC. Global fitting of multiple data frames from SEC–SAXS to investigate the structure of next-generation nanodiscs. Acta Crystallogr D Struct Biol 2022; 78:483-493. [PMID: 35362471 PMCID: PMC8972807 DOI: 10.1107/s2059798322001838] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/08/2021] [Accepted: 02/16/2022] [Indexed: 11/10/2022]
Abstract
The combination of online size-exclusion chromatography and small-angle X-ray scattering (SEC–SAXS) is rapidly becoming a key technique for structural investigations of elaborate biophysical samples in solution. Here, a novel model-refinement strategy centred around the technique is outlined and its utility is demonstrated by analysing data series from several SEC–SAXS experiments on phospholipid bilayer nanodiscs. Using this method, a single model was globally refined against many frames from the same data series, thereby capturing the frame-to-frame tendencies of the irradiated sample. These are compared with models refined in the traditional manner, in which refinement is based on the average profile of a set of consecutive frames from the same data series without an in-depth comparison of individual frames. This is considered to be an attractive model-refinement scheme as it considerably lowers the total number of parameters refined from the data series, produces tendencies that are automatically consistent between frames, and utilizes a considerably larger portion of the recorded data than is often performed in such experiments. Additionally, a method is outlined for correcting a measured UV absorption signal by accounting for potential peak broadening by the experimental setup.
Collapse
|
10
|
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.
Collapse
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
| |
Collapse
|
11
|
Zampieri V, Gobet A, Robert X, Falson P, Chaptal V. CryoEM reconstructions of membrane proteins solved in several amphipathic solvents, nanodisc, amphipol and detergents, yield amphipathic belts of similar sizes corresponding to a common ordered solvent layer. Biochim Biophys Acta Biomembr 2021;:183693. [PMID: 34271006 DOI: 10.1016/j.bbamem.2021.183693] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 04/27/2021] [Revised: 06/28/2021] [Accepted: 06/30/2021] [Indexed: 12/31/2022]
Abstract
To maintain membrane proteins soluble in aqueous solution, amphipathic compounds are used to shield the hydrophobic patch of their membrane insertion, which forms a belt around the protein. This amphipathic belt is seldom looked at due to the difficulty to visualize it. Cryo-EM is now offering this possibility, where belts are visible in 3D reconstructions. We investigated membrane proteins solved in nanodiscs, amphipols or detergents to analyze whether the nature of the amphipathic compound influences the belt size in 3D reconstructions. We identified belt boundaries in map-density distributions and measured distances for every reconstruction. We showed that all the belts create on average similar reconstructions, whether they originate from the same protein, or from protein from different shapes and structures. There is no difference among detergents or types of nanodisc used. These observations illustrate that the belt observed in 3D reconstructions corresponds to the minimum ordered layer around membrane proteins.
Collapse
|