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Lane BJ, Ma Y, Yan N, Wang B, Ackermann K, Karamanos TK, Bode BE, Pliotas C. Monitoring the conformational ensemble and lipid environment of a mechanosensitive channel under cyclodextrin-induced membrane tension. Structure 2024:S0969-2126(24)00080-7. [PMID: 38521071 DOI: 10.1016/j.str.2024.02.020] [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: 09/14/2023] [Revised: 12/29/2023] [Accepted: 02/27/2024] [Indexed: 03/25/2024]
Abstract
Membrane forces shift the equilibria of mechanosensitive channels enabling them to convert mechanical cues into electrical signals. Molecular tools to stabilize and methods to capture their highly dynamic states are lacking. Cyclodextrins can mimic tension through the sequestering of lipids from membranes. Here we probe the conformational ensemble of MscS by EPR spectroscopy, the lipid environment with NMR, and function with electrophysiology under cyclodextrin-induced tension. We show the extent of MscS activation depends on the cyclodextrin-to-lipid ratio, and that lipids are depleted slower when MscS is present. This has implications in MscS' activation kinetics when distinct membrane scaffolds such as nanodiscs or liposomes are used. We find MscS transits from closed to sub-conducting state(s) before it desensitizes, due to the lack of lipid availability in its vicinity required for closure. Our approach allows for monitoring tension-sensitive states in membrane proteins and screening molecules capable of inducing molecular tension in bilayers.
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Affiliation(s)
- Benjamin J Lane
- Astbury Centre for Structural Molecular Biology, School of Biomedical Sciences, University of Leeds, Leeds LS2 9JT, UK
| | - Yue Ma
- School of Biological Sciences, Faculty of Biology, Medicine and Health, Manchester Academic and Health Science Centre, The University of Manchester, Manchester M13 9PT, UK
| | - Nana Yan
- Astbury Centre for Structural Molecular Biology, School of Biomedical Sciences, University of Leeds, Leeds LS2 9JT, UK
| | - Bolin Wang
- School of Biological Sciences, Faculty of Biology, Medicine and Health, Manchester Academic and Health Science Centre, The University of Manchester, Manchester M13 9PT, UK
| | - Katrin Ackermann
- EaStCHEM School of Chemistry, Biomedical Sciences Research Complex and Centre of Magnetic Resonance, University of St Andrews, St Andrews KY16 9ST, UK
| | - Theodoros K Karamanos
- Department of Life Sciences, Faculty of Natural Sciences, Imperial College London, London SW7 2AZ, UK
| | - Bela E Bode
- EaStCHEM School of Chemistry, Biomedical Sciences Research Complex and Centre of Magnetic Resonance, University of St Andrews, St Andrews KY16 9ST, UK
| | - Christos Pliotas
- Astbury Centre for Structural Molecular Biology, School of Biomedical Sciences, University of Leeds, Leeds LS2 9JT, UK; School of Biological Sciences, Faculty of Biology, Medicine and Health, Manchester Academic and Health Science Centre, The University of Manchester, Manchester M13 9PT, UK; Manchester Institute of Biotechnology, The University of Manchester, Manchester M1 7DN, UK.
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2
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Haysom SF, Machin J, Whitehouse JM, Horne JE, Fenn K, Ma Y, El Mkami H, Böhringer N, Schäberle TF, Ranson NA, Radford SE, Pliotas C. Darobactin B Stabilises a Lateral-Closed Conformation of the BAM Complex in E. coli Cells. Angew Chem Weinheim Bergstr Ger 2023; 135:e202218783. [PMID: 38515502 PMCID: PMC10952338 DOI: 10.1002/ange.202218783] [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] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/19/2022] [Indexed: 03/23/2024]
Abstract
The β-barrel assembly machinery (BAM complex) is essential for outer membrane protein (OMP) folding in Gram-negative bacteria, and represents a promising antimicrobial target. Several conformational states of BAM have been reported, but all have been obtained under conditions which lack the unique features and complexity of the outer membrane (OM). Here, we use Pulsed Electron-Electron Double Resonance (PELDOR, or DEER) spectroscopy distance measurements to interrogate the conformational ensemble of the BAM complex in E. coli cells. We show that BAM adopts a broad ensemble of conformations in the OM, while in the presence of the antibiotic darobactin B (DAR-B), BAM's conformational equilibrium shifts to a restricted ensemble consistent with the lateral closed state. Our in-cell PELDOR findings are supported by new cryoEM structures of BAM in the presence and absence of DAR-B. This work demonstrates the utility of PELDOR to map conformational changes in BAM within its native cellular environment.
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Affiliation(s)
- Samuel F. Haysom
- Astbury Centre for Structural Molecular BiologySchool of Molecular and Cellular BiologyUniversity of LeedsLeedsLS2 9JTUK
| | - Jonathan Machin
- Astbury Centre for Structural Molecular BiologySchool of Molecular and Cellular BiologyUniversity of LeedsLeedsLS2 9JTUK
| | - James M. Whitehouse
- Astbury Centre for Structural Molecular BiologySchool of Molecular and Cellular BiologyUniversity of LeedsLeedsLS2 9JTUK
| | - Jim E. Horne
- Astbury Centre for Structural Molecular BiologySchool of Molecular and Cellular BiologyUniversity of LeedsLeedsLS2 9JTUK
| | - Katherine Fenn
- Astbury Centre for Structural Molecular BiologySchool of Molecular and Cellular BiologyUniversity of LeedsLeedsLS2 9JTUK
| | - Yue Ma
- Astbury Centre for Structural Molecular BiologySchool of Biomedical SciencesUniversity of LeedsLeedsLS2 9JTUK
- School of Biological Sciences, Faculty of Biology, Medicine and HealthManchester Academic and Health Science CentreThe University of ManchesterManchesterM13 9PTUK
- Manchester Institute of BiotechnologyThe University of ManchesterManchesterM1 7DNUK
| | - Hassane El Mkami
- School of Physics and AstronomyUniversity of St. AndrewsSt. AndrewsKY16 9SSUK
| | - Nils Böhringer
- Institute for Insect BiotechnologyNatural Product ResearchJustus-Liebig-University GiessenOhlebergsweg 1235392GiessenGermany
- German Center for Infection Research (DZIF)Partner Site Giessen-Marburg-LangenOhlebergsweg 1235392GiessenGermany
| | - Till F. Schäberle
- Institute for Insect BiotechnologyNatural Product ResearchJustus-Liebig-University GiessenOhlebergsweg 1235392GiessenGermany
- German Center for Infection Research (DZIF)Partner Site Giessen-Marburg-LangenOhlebergsweg 1235392GiessenGermany
- Natural Product DepartmentFraunhofer-Institute for Molecular Biology and Applied Ecology (IME)Ohlebergsweg 1235392GiessenGermany
| | - Neil A. Ranson
- Astbury Centre for Structural Molecular BiologySchool of Molecular and Cellular BiologyUniversity of LeedsLeedsLS2 9JTUK
| | - Sheena E. Radford
- Astbury Centre for Structural Molecular BiologySchool of Molecular and Cellular BiologyUniversity of LeedsLeedsLS2 9JTUK
| | - Christos Pliotas
- Astbury Centre for Structural Molecular BiologySchool of Biomedical SciencesUniversity of LeedsLeedsLS2 9JTUK
- School of Biological Sciences, Faculty of Biology, Medicine and HealthManchester Academic and Health Science CentreThe University of ManchesterManchesterM13 9PTUK
- Manchester Institute of BiotechnologyThe University of ManchesterManchesterM1 7DNUK
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3
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Haysom SF, Machin J, Whitehouse JM, Horne JE, Fenn K, Ma Y, El Mkami H, Böhringer N, Schäberle TF, Ranson NA, Radford SE, Pliotas C. Darobactin B Stabilises a Lateral-Closed Conformation of the BAM Complex in E. coli Cells. Angew Chem Int Ed Engl 2023; 62:e202218783. [PMID: 37162386 PMCID: PMC10952311 DOI: 10.1002/anie.202218783] [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] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2022] [Revised: 04/26/2023] [Accepted: 05/09/2023] [Indexed: 05/11/2023]
Abstract
The β-barrel assembly machinery (BAM complex) is essential for outer membrane protein (OMP) folding in Gram-negative bacteria, and represents a promising antimicrobial target. Several conformational states of BAM have been reported, but all have been obtained under conditions which lack the unique features and complexity of the outer membrane (OM). Here, we use Pulsed Electron-Electron Double Resonance (PELDOR, or DEER) spectroscopy distance measurements to interrogate the conformational ensemble of the BAM complex in E. coli cells. We show that BAM adopts a broad ensemble of conformations in the OM, while in the presence of the antibiotic darobactin B (DAR-B), BAM's conformational equilibrium shifts to a restricted ensemble consistent with the lateral closed state. Our in-cell PELDOR findings are supported by new cryoEM structures of BAM in the presence and absence of DAR-B. This work demonstrates the utility of PELDOR to map conformational changes in BAM within its native cellular environment.
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Affiliation(s)
- Samuel F. Haysom
- Astbury Centre for Structural Molecular BiologySchool of Molecular and Cellular BiologyUniversity of LeedsLeedsLS2 9JTUK
| | - Jonathan Machin
- Astbury Centre for Structural Molecular BiologySchool of Molecular and Cellular BiologyUniversity of LeedsLeedsLS2 9JTUK
| | - James M. Whitehouse
- Astbury Centre for Structural Molecular BiologySchool of Molecular and Cellular BiologyUniversity of LeedsLeedsLS2 9JTUK
| | - Jim E. Horne
- Astbury Centre for Structural Molecular BiologySchool of Molecular and Cellular BiologyUniversity of LeedsLeedsLS2 9JTUK
| | - Katherine Fenn
- Astbury Centre for Structural Molecular BiologySchool of Molecular and Cellular BiologyUniversity of LeedsLeedsLS2 9JTUK
| | - Yue Ma
- Astbury Centre for Structural Molecular BiologySchool of Biomedical SciencesUniversity of LeedsLeedsLS2 9JTUK
- School of Biological Sciences, Faculty of Biology, Medicine and HealthManchester Academic and Health Science CentreThe University of ManchesterManchesterM13 9PTUK
- Manchester Institute of BiotechnologyThe University of ManchesterManchesterM1 7DNUK
| | - Hassane El Mkami
- School of Physics and AstronomyUniversity of St. AndrewsSt. AndrewsKY16 9SSUK
| | - Nils Böhringer
- Institute for Insect BiotechnologyNatural Product ResearchJustus-Liebig-University GiessenOhlebergsweg 1235392GiessenGermany
- German Center for Infection Research (DZIF)Partner Site Giessen-Marburg-LangenOhlebergsweg 1235392GiessenGermany
| | - Till F. Schäberle
- Institute for Insect BiotechnologyNatural Product ResearchJustus-Liebig-University GiessenOhlebergsweg 1235392GiessenGermany
- German Center for Infection Research (DZIF)Partner Site Giessen-Marburg-LangenOhlebergsweg 1235392GiessenGermany
- Natural Product DepartmentFraunhofer-Institute for Molecular Biology and Applied Ecology (IME)Ohlebergsweg 1235392GiessenGermany
| | - Neil A. Ranson
- Astbury Centre for Structural Molecular BiologySchool of Molecular and Cellular BiologyUniversity of LeedsLeedsLS2 9JTUK
| | - Sheena E. Radford
- Astbury Centre for Structural Molecular BiologySchool of Molecular and Cellular BiologyUniversity of LeedsLeedsLS2 9JTUK
| | - Christos Pliotas
- Astbury Centre for Structural Molecular BiologySchool of Biomedical SciencesUniversity of LeedsLeedsLS2 9JTUK
- School of Biological Sciences, Faculty of Biology, Medicine and HealthManchester Academic and Health Science CentreThe University of ManchesterManchesterM13 9PTUK
- Manchester Institute of BiotechnologyThe University of ManchesterManchesterM1 7DNUK
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4
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Lane BJ, Pliotas C. Approaches for the modulation of mechanosensitive MscL channel pores. Front Chem 2023; 11:1162412. [PMID: 37021145 PMCID: PMC10069478 DOI: 10.3389/fchem.2023.1162412] [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] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2023] [Accepted: 03/03/2023] [Indexed: 03/17/2023] Open
Abstract
MscL was the first mechanosensitive ion channel identified in bacteria. The channel opens its large pore when the turgor pressure of the cytoplasm increases close to the lytic limit of the cellular membrane. Despite their ubiquity across organisms, their importance in biological processes, and the likelihood that they are one of the oldest mechanisms of sensory activation in cells, the exact molecular mechanism by which these channels sense changes in lateral tension is not fully understood. Modulation of the channel has been key to understanding important aspects of the structure and function of MscL, but a lack of molecular triggers of these channels hindered early developments in the field. Initial attempts to activate mechanosensitive channels and stabilize functionally relevant expanded or open states relied on mutations and associated post-translational modifications that were often cysteine reactive. These sulfhydryl reagents positioned at key residues have allowed the engineering of MscL channels for biotechnological purposes. Other studies have modulated MscL by altering membrane properties, such as lipid composition and physical properties. More recently, a variety of structurally distinct agonists have been shown bind to MscL directly, close to a transmembrane pocket that has been shown to have an important role in channel mechanical gating. These agonists have the potential to be developed further into antimicrobial therapies that target MscL, by considering the structural landscape and properties of these pockets.
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Affiliation(s)
- Benjamin J. Lane
- Astbury Centre for Structural Molecular Biology, School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
| | - Christos Pliotas
- Astbury Centre for Structural Molecular Biology, School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
- School of Biological Sciences, Faculty of Biology, Medicine and Health, Manchester Academic and Health Science Centre, The University of Manchester, Manchester, United Kingdom
- Manchester Institute of Biotechnology, The University of Manchester, Manchester, United Kingdom
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5
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Dionysopoulou M, Yan N, Wang B, Pliotas C, Diallinas G. Genetic and cellular characterization of MscS-like putative channels in the filamentous fungus Aspergillus nidulans. Channels (Austin) 2022; 16:148-158. [PMID: 35941834 PMCID: PMC9367656 DOI: 10.1080/19336950.2022.2098661] [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] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Mechanosensitive ion channels are integral membrane proteins ubiquitously present in bacteria, archaea, and eukarya. They act as molecular sensors of mechanical stress to serve vital functions such as touch, hearing, osmotic pressure, proprioception and balance, while their malfunction is often associated with pathologies. Amongst them, the structurally distinct MscL and MscS channels from bacteria are the most extensively studied. MscS-like channels have been found in plants and Schizosaccharomyces pombe, where they regulate intracellular Ca2+ and cell volume under hypo-osmotic conditions. Here we characterize two MscS-like putative channels, named MscA and MscB, from the model filamentous fungus Aspergillus nidulans. Orthologues of MscA and MscB are present in most fungi, including relative plant and animal pathogens. MscA/MscB and other fungal MscS-like proteins share the three transmembrane helices and the extended C-terminal cytosolic domain that form the structural fingerprint of MscS-like channels with at least three additional transmembrane segments than Escherichia coli MscS. We show that MscA and MscB localize in Endoplasmic Reticulum and the Plasma Membrane, respectively, whereas their overexpression leads to increased CaCl2 toxicity or/and reduction of asexual spore formation. Our findings contribute to understanding the role of MscS-like channels in filamentous fungi and relative pathogens.
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Affiliation(s)
- Mariangela Dionysopoulou
- Astbury Centre for Structural Molecular Biology, School of Biomedical Sciences, University of Leeds, LS2 9JT, Leeds, United Kingdom.,Department of Biology, National and Kapodistrian University of Athens, Panepistimioupolis, 15784 Athens, Greece
| | - Nana Yan
- Astbury Centre for Structural Molecular Biology, School of Biomedical Sciences, University of Leeds, LS2 9JT, Leeds, United Kingdom
| | - Bolin Wang
- Astbury Centre for Structural Molecular Biology, School of Biomedical Sciences, University of Leeds, LS2 9JT, Leeds, United Kingdom
| | - Christos Pliotas
- Astbury Centre for Structural Molecular Biology, School of Biomedical Sciences, University of Leeds, LS2 9JT, Leeds, United Kingdom
| | - George Diallinas
- Department of Biology, National and Kapodistrian University of Athens, Panepistimioupolis, 15784 Athens, Greece.,Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology, 70013 Heraklion, Greece
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6
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Boakes JC, Harborne SPD, Ngo JTS, Pliotas C, Goldman A. Novel variants provide differential stabilisation of human equilibrative nucleoside transporter 1 states. Front Mol Biosci 2022; 9:970391. [DOI: 10.3389/fmolb.2022.970391] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Accepted: 10/27/2022] [Indexed: 11/10/2022] Open
Abstract
Human equilibrative nucleoside transporters represent a major pharmaceutical target for cardiac, cancer and viral therapies. Understanding the molecular basis for transport is crucial for the development of improved therapeutics through structure-based drug design. ENTs have been proposed to utilise an alternating access mechanism of action, similar to that of the major facilitator superfamily. However, ENTs lack functionally-essential features of that superfamily, suggesting that they may use a different transport mechanism. Understanding the molecular basis of their transport requires insight into diverse conformational states. Differences between intermediate states may be discrete and mediated by subtle gating interactions, such as salt bridges. We identified four variants of human equilibrative nucleoside transporter isoform 1 (hENT1) at the large intracellular loop (ICL6) and transmembrane helix 7 (TM7) that stabilise the apo-state (∆Tm 0.7–1.5°C). Furthermore, we showed that variants K263A (ICL6) and I282V (TM7) specifically stabilise the inhibitor-bound state of hENT1 (∆∆Tm 5.0 ± 1.7°C and 3.0 ± 1.8°C), supporting the role of ICL6 in hENT1 gating. Finally, we showed that, in comparison with wild type, variant T336A is destabilised by nitrobenzylthioinosine (∆∆Tm -4.7 ± 1.1°C) and binds it seven times worse. This residue may help determine inhibitor and substrate sensitivity. Residue K263 is not present in the solved structures, highlighting the need for further structural data that include the loop regions.
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7
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Lane BJ, Wang B, Ma Y, Calabrese AN, El Mkami H, Pliotas C. HDX-guided EPR spectroscopy to interrogate membrane protein dynamics. STAR Protoc 2022; 3:101562. [PMID: 35874470 PMCID: PMC9304679 DOI: 10.1016/j.xpro.2022.101562] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Solvent accessibilities of and distances between protein residues measured by pulsed-EPR approaches provide high-resolution information on dynamic protein motions. We describe protocols for the purification and site-directed spin labeling of integral membrane proteins. In our protocol, peptide-level HDX-MS is used as a precursor to guide single-residue resolution ESEEM accessibility measurements and spin labeling strategies for EPR applications. Exploiting the pentameric MscL channel as a model, we discuss the use of cwEPR, DEER/PELDOR, and ESEEM spectroscopies to interrogate membrane protein dynamics. For complete details on the use and execution of this protocol, please refer to Wang et al. (2022). Protocols for an integrated EPR-based approach to study membrane protein dynamics Instructions for the sample preparation of spin-labeled membrane proteins Used HDX-MS as a precursor to guide spin labeling strategies for EPR methods Probed solvent accessibility at the single-residue level by ESEEM
Publisher’s note: Undertaking any experimental protocol requires adherence to local institutional guidelines for laboratory safety and ethics.
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Wang B, Lane BJ, Kapsalis C, Ault JR, Sobott F, El Mkami H, Calabrese AN, Kalli AC, Pliotas C. Pocket delipidation induced by membrane tension or modification leads to a structurally analogous mechanosensitive channel state. Structure 2022; 30:608-622.e5. [PMID: 34986323 PMCID: PMC9033278 DOI: 10.1016/j.str.2021.12.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2021] [Revised: 10/13/2021] [Accepted: 12/07/2021] [Indexed: 01/06/2023]
Abstract
The mechanosensitive ion channel of large conductance MscL gates in response to membrane tension changes. Lipid removal from transmembrane pockets leads to a concerted structural and functional MscL response, but it remains unknown whether there is a correlation between the tension-mediated state and the state derived by pocket delipidation in the absence of tension. Here, we combined pulsed electron paramagnetic resonance spectroscopy and hydrogen-deuterium exchange mass spectrometry, coupled with molecular dynamics simulations under membrane tension, to investigate the structural changes associated with the distinctively derived states. Whether it is tension- or modification-mediated pocket delipidation, we find that MscL samples a similar expanded subconducting state. This is the final step of the delipidation pathway, but only an intermediate stop on the tension-mediated path, with additional tension triggering further channel opening. Our findings hint at synergistic modes of regulation by lipid molecules in membrane tension-activated mechanosensitive channels.
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Affiliation(s)
- Bolin Wang
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK; School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK
| | - Benjamin J Lane
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK; School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK
| | - Charalampos Kapsalis
- Biomedical Sciences Research Complex, School of Biology, University of St Andrews, St Andrews KY16 9ST, UK
| | - James R Ault
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK; School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK
| | - Frank Sobott
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK; School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK
| | - Hassane El Mkami
- School of Physics and Astronomy, University of St Andrews, St Andrews KY16 9SS, UK
| | - Antonio N Calabrese
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK; School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK
| | - Antreas C Kalli
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK; Leeds Institute of Cardiovascular and Metabolic Medicine, School of Medicine, University of Leeds, Leeds LS2 9NL, UK
| | - Christos Pliotas
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK; School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK; Biomedical Sciences Research Complex, School of Biology, University of St Andrews, St Andrews KY16 9ST, UK.
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9
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Koo CZ, Harrison N, Noy PJ, Szyroka J, Matthews AL, Hsia HE, Müller SA, Tüshaus J, Goulding J, Willis K, Apicella C, Cragoe B, Davis E, Keles M, Malinova A, McFarlane TA, Morrison PR, Nguyen HTH, Sykes MC, Ahmed H, Di Maio A, Seipold L, Saftig P, Cull E, Pliotas C, Rubinstein E, Poulter NS, Briddon SJ, Holliday ND, Lichtenthaler SF, Tomlinson MG. The tetraspanin Tspan15 is an essential subunit of an ADAM10 scissor complex. J Biol Chem 2020; 295:12822-12839. [PMID: 32111735 PMCID: PMC7476718 DOI: 10.1074/jbc.ra120.012601] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2020] [Revised: 02/14/2020] [Indexed: 12/13/2022] Open
Abstract
A disintegrin and metalloprotease 10 (ADAM10) is a transmembrane protein essential for embryonic development, and its dysregulation underlies disorders such as cancer, Alzheimer's disease, and inflammation. ADAM10 is a "molecular scissor" that proteolytically cleaves the extracellular region from >100 substrates, including Notch, amyloid precursor protein, cadherins, growth factors, and chemokines. ADAM10 has been recently proposed to function as six distinct scissors with different substrates, depending on its association with one of six regulatory tetraspanins, termed TspanC8s. However, it remains unclear to what degree ADAM10 function critically depends on a TspanC8 partner, and a lack of monoclonal antibodies specific for most TspanC8s has hindered investigation of this question. To address this knowledge gap, here we designed an immunogen to generate the first monoclonal antibodies targeting Tspan15, a model TspanC8. The immunogen was created in an ADAM10-knockout mouse cell line stably overexpressing human Tspan15, because we hypothesized that expression in this cell line would expose epitopes that are normally blocked by ADAM10. Following immunization of mice, this immunogen strategy generated four Tspan15 antibodies. Using these antibodies, we show that endogenous Tspan15 and ADAM10 co-localize on the cell surface, that ADAM10 is the principal Tspan15-interacting protein, that endogenous Tspan15 expression requires ADAM10 in cell lines and primary cells, and that a synthetic ADAM10/Tspan15 fusion protein is a functional scissor. Furthermore, two of the four antibodies impaired ADAM10/Tspan15 activity. These findings suggest that Tspan15 directly interacts with ADAM10 in a functional scissor complex.
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Affiliation(s)
- Chek Ziu Koo
- School of Biosciences, University of Birmingham, Birmingham B15 2TT, United Kingdom
- Centre of Membrane Proteins and Receptors (COMPARE), Universities of Birmingham and Nottingham, Midlands B15 2TT, United Kingdom
| | - Neale Harrison
- School of Biosciences, University of Birmingham, Birmingham B15 2TT, United Kingdom
| | - Peter J Noy
- School of Biosciences, University of Birmingham, Birmingham B15 2TT, United Kingdom
| | - Justyna Szyroka
- School of Biosciences, University of Birmingham, Birmingham B15 2TT, United Kingdom
| | - Alexandra L Matthews
- School of Biosciences, University of Birmingham, Birmingham B15 2TT, United Kingdom
| | - Hung-En Hsia
- German Center for Neurodegenerative Diseases (DZNE) Munich, Neuroproteomics, Klinikum rechts der Isar, Technical University Munich and Munich Cluster for Systems Neurology (SyNergy), 81377 Munich, Germany
| | - Stephan A Müller
- German Center for Neurodegenerative Diseases (DZNE) Munich, Neuroproteomics, Klinikum rechts der Isar, Technical University Munich and Munich Cluster for Systems Neurology (SyNergy), 81377 Munich, Germany
| | - Johanna Tüshaus
- German Center for Neurodegenerative Diseases (DZNE) Munich, Neuroproteomics, Klinikum rechts der Isar, Technical University Munich and Munich Cluster for Systems Neurology (SyNergy), 81377 Munich, Germany
| | - Joelle Goulding
- Centre of Membrane Proteins and Receptors (COMPARE), Universities of Birmingham and Nottingham, Midlands B15 2TT, United Kingdom
- Division of Physiology, Pharmacology and Neuroscience, School of Life Sciences, University of Nottingham, Nottingham NG7 2UH, United Kingdom
| | - Katie Willis
- School of Biosciences, University of Birmingham, Birmingham B15 2TT, United Kingdom
| | - Clara Apicella
- School of Biosciences, University of Birmingham, Birmingham B15 2TT, United Kingdom
| | - Bethany Cragoe
- School of Biosciences, University of Birmingham, Birmingham B15 2TT, United Kingdom
| | - Edward Davis
- School of Biosciences, University of Birmingham, Birmingham B15 2TT, United Kingdom
| | - Murat Keles
- School of Biosciences, University of Birmingham, Birmingham B15 2TT, United Kingdom
| | - Antonia Malinova
- School of Biosciences, University of Birmingham, Birmingham B15 2TT, United Kingdom
| | - Thomas A McFarlane
- School of Biosciences, University of Birmingham, Birmingham B15 2TT, United Kingdom
| | - Philip R Morrison
- School of Biosciences, University of Birmingham, Birmingham B15 2TT, United Kingdom
| | - Hanh T H Nguyen
- School of Biosciences, University of Birmingham, Birmingham B15 2TT, United Kingdom
| | - Michael C Sykes
- School of Biosciences, University of Birmingham, Birmingham B15 2TT, United Kingdom
| | - Haroon Ahmed
- School of Biosciences, University of Birmingham, Birmingham B15 2TT, United Kingdom
| | - Alessandro Di Maio
- School of Biosciences, University of Birmingham, Birmingham B15 2TT, United Kingdom
| | - Lisa Seipold
- Institute of Biochemistry, Christian Albrechts University Kiel, 24118 Kiel, Germany
| | - Paul Saftig
- Institute of Biochemistry, Christian Albrechts University Kiel, 24118 Kiel, Germany
| | - Eleanor Cull
- School of Biosciences, University of Birmingham, Birmingham B15 2TT, United Kingdom
| | - Christos Pliotas
- School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Eric Rubinstein
- Sorbonne Université, INSERM, CNRS, Centre d'Immunologie et des Maladies Infectieuses, CIMI-Paris, Paris 75013, France
| | - Natalie S Poulter
- Centre of Membrane Proteins and Receptors (COMPARE), Universities of Birmingham and Nottingham, Midlands B15 2TT, United Kingdom
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham B15 2TT, United Kingdom
| | - Stephen J Briddon
- Centre of Membrane Proteins and Receptors (COMPARE), Universities of Birmingham and Nottingham, Midlands B15 2TT, United Kingdom
- Division of Physiology, Pharmacology and Neuroscience, School of Life Sciences, University of Nottingham, Nottingham NG7 2UH, United Kingdom
| | - Nicholas D Holliday
- Division of Physiology, Pharmacology and Neuroscience, School of Life Sciences, University of Nottingham, Nottingham NG7 2UH, United Kingdom
| | - Stefan F Lichtenthaler
- German Center for Neurodegenerative Diseases (DZNE) Munich, Neuroproteomics, Klinikum rechts der Isar, Technical University Munich and Munich Cluster for Systems Neurology (SyNergy), 81377 Munich, Germany
| | - Michael G Tomlinson
- School of Biosciences, University of Birmingham, Birmingham B15 2TT, United Kingdom
- Centre of Membrane Proteins and Receptors (COMPARE), Universities of Birmingham and Nottingham, Midlands B15 2TT, United Kingdom
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10
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Kapsalis C, Ma Y, Bode BE, Pliotas C. In-Lipid Structure of Pressure-Sensitive Domains Hints Mechanosensitive Channel Functional Diversity. Biophys J 2020; 119:448-459. [PMID: 32621864 PMCID: PMC7376121 DOI: 10.1016/j.bpj.2020.06.012] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Revised: 06/03/2020] [Accepted: 06/10/2020] [Indexed: 11/30/2022] Open
Abstract
The mechanosensitive channel of large conductance (MscL) from Mycobacterium tuberculosis has been used as a structural model for rationalizing functional observations in multiple MscL orthologs. Although these orthologs adopt similar structural architectures, they reportedly present significant functional differences. Subtle structural discrepancies on mechanosensitive channel nanopockets are known to affect mechanical gating and may be linked to large variability in tension sensitivity among these membrane channels. Here, we modify the nanopocket regions of MscL from Escherichia coli and M. tuberculosis and employ PELDOR/DEER distance and 3pESEEM deuterium accessibility measurements to interrogate channel structure within lipids, in which both channels adopt a closed conformation. Significant in-lipid structural differences between the two constructs suggest a more compact E. coli MscL at the membrane inner-leaflet, as a consequence of a rotated TM2 helix. Observed differences within lipids could explain E. coli MscL’s higher tension sensitivity and should be taken into account in extrapolated models used for MscL gating rationalization.
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Affiliation(s)
- Charalampos Kapsalis
- Biomedical Sciences Research Complex, School of Biology, University of St Andrews, St Andrews, United Kingdom
| | - Yue Ma
- Astbury Centre for Structural and Molecular Biology, University of Leeds, Leeds, United Kingdom; School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
| | - Bela E Bode
- Biomedical Sciences Research Complex, School of Chemistry, University of St Andrews, St Andrews, United Kingdom.
| | - Christos Pliotas
- Biomedical Sciences Research Complex, School of Biology, University of St Andrews, St Andrews, United Kingdom; Astbury Centre for Structural and Molecular Biology, University of Leeds, Leeds, United Kingdom; School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom.
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11
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Michou M, Kapsalis C, Pliotas C, Skretas G. Optimization of Recombinant Membrane Protein Production in the Engineered Escherichia coli Strains SuptoxD and SuptoxR. ACS Synth Biol 2019; 8:1631-1641. [PMID: 31243979 DOI: 10.1021/acssynbio.9b00120] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Membrane proteins (MPs) execute a wide variety of critical biological functions in all living organisms and constitute approximately half of current targets for drug discovery. As in the case of soluble proteins, the bacterium Escherichia coli has served as a very popular overexpression host for biochemical/structural studies of membrane proteins as well. Bacterial recombinant membrane protein production, however, is typically hampered by poor cellular accumulation and severe toxicity for the host, which leads to low levels of final biomass and minute volumetric yields. In previous work, we generated the engineered E. coli strains SuptoxD and SuptoxR, which upon coexpression of the effector genes djlA or rraA, respectively, can suppress the cytotoxicity caused by MP overexpression and produce enhanced MP yields. Here, we systematically looked for gene overexpression and culturing conditions that maximize the accumulation of membrane-integrated and well-folded recombinant MPs in these strains. We have found that, under optimal conditions, SuptoxD and SuptoxR achieve greatly enhanced recombinant production for a variety of MP, irrespective of their archaeal, eubacterial, or eukaryotic origin. Furthermore, we demonstrate that the use of these engineered strains enables the production of well-folded recombinant MPs of high quality and at high yields, which are suitable for functional and structural studies. We anticipate that SuptoxD and SuptoxR will become broadly utilized expression hosts for recombinant MP production in bacteria.
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Affiliation(s)
- Myrsini Michou
- Institute of Chemical Biology, National Hellenic Research Foundation, Athens 11635, Greece
- Department of Biochemistry and Biotechnology, University of Thessaly, Viopolis, Larisa 41500, Greece
| | - Charalampos Kapsalis
- Biomedical Sciences Research Complex, School of Biology, University of St Andrews, St Andrews KY169ST, United Kingdom
| | - Christos Pliotas
- Biomedical Sciences Research Complex, School of Biology, University of St Andrews, St Andrews KY169ST, United Kingdom
- Astbury Centre for Structural Molecular Biology, School of Biomedical Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Georgios Skretas
- Institute of Chemical Biology, National Hellenic Research Foundation, Athens 11635, Greece
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12
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Harborne S, Shah N, Wilkinson C, Pliotas C, Harris S, Tuma R, Goldman A. What we have learned about membrane-bound pyrophosphatases (mPPases) from X-ray crystallography, MD simulations, FRET and PELDOR. Acta Crystallogr A Found Adv 2018. [DOI: 10.1107/s2053273318094718] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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13
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Ackermann K, Pliotas C, Valera S, Naismith JH, Bode BE. Sparse Labeling PELDOR Spectroscopy on Multimeric Mechanosensitive Membrane Channels. Biophys J 2017; 113:1968-1978. [PMID: 29117521 PMCID: PMC5685675 DOI: 10.1016/j.bpj.2017.09.005] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2017] [Revised: 08/31/2017] [Accepted: 09/05/2017] [Indexed: 11/17/2022] Open
Abstract
Pulse electron paramagnetic resonance (EPR) is being applied to ever more complex biological systems comprising multiple subunits. Membrane channel proteins are of great interest as pulse EPR reports on functionally significant but distinct conformational states in a native environment without the need for crystallization. Pulse EPR, in the form of pulsed electron-electron double resonance (PELDOR), using site-directed spin labeling, is most commonly employed to accurately determine distances (in the nanometer range) between different regions of the structure. However, PELDOR data analysis is more challenging in systems containing more than two spins (e.g., homomultimers) due to distorting multispin effects. Without suppression of these effects, much of the information contained in PELDOR data cannot be reliably retrieved. Thus, it is of utmost importance for future PELDOR applications in structural biology to develop suitable approaches that can overcome the multispin problem. Here, two different approaches for suppressing multispin effects in PELDOR, sparse labeling of the protein (reducing the labeling efficiency f) and reducing the excitation probability of spins (λ), are compared on two distinct bacterial mechanosensitive channels. For both the pentameric channel of large conductance (MscL) and the heptameric channel of small conductance (MscS) of Escherichia coli, mutants containing a spin label in the cytosolic or the transmembrane region were tested. Data demonstrate that distance distributions can be significantly improved with either approach compared to the standard PELDOR measurement, and confirm that λ < 1/(n−1) is needed to sufficiently suppress multispin effects (with n being the number of spins in the system). A clear advantage of the sparse labeling approach is demonstrated for the cytosolic mutants due to a significantly smaller loss in sensitivity. For the transmembrane mutants, this advantage is less pronounced but still useful for MscS, but performance is inferior for MscL possibly due to structural perturbations by the bulkier diamagnetic spin label analog.
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Affiliation(s)
- Katrin Ackermann
- Centre of Magnetic Resonance, University of St Andrews, North Haugh, St Andrews, Fife, United Kingdom; Biomedical Sciences Research Complex and EaStCHEM School of Chemistry, University of St Andrews, North Haugh, St Andrews, Fife, United Kingdom
| | - Christos Pliotas
- Centre of Magnetic Resonance, University of St Andrews, North Haugh, St Andrews, Fife, United Kingdom; Biomedical Sciences Research Complex and EaStCHEM School of Chemistry, University of St Andrews, North Haugh, St Andrews, Fife, United Kingdom
| | - Silvia Valera
- Centre of Magnetic Resonance, University of St Andrews, North Haugh, St Andrews, Fife, United Kingdom; Biomedical Sciences Research Complex and EaStCHEM School of Chemistry, University of St Andrews, North Haugh, St Andrews, Fife, United Kingdom
| | - James H Naismith
- Biomedical Sciences Research Complex and EaStCHEM School of Chemistry, University of St Andrews, North Haugh, St Andrews, Fife, United Kingdom
| | - Bela E Bode
- Centre of Magnetic Resonance, University of St Andrews, North Haugh, St Andrews, Fife, United Kingdom; Biomedical Sciences Research Complex and EaStCHEM School of Chemistry, University of St Andrews, North Haugh, St Andrews, Fife, United Kingdom.
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14
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Pliotas C, Grayer SC, Ekkerman S, Chan AKN, Healy J, Marius P, Bartlett W, Khan A, Cortopassi WA, Chandler SA, Rasmussen T, Benesch JLP, Paton RS, Claridge TDW, Miller S, Booth IR, Naismith JH, Conway SJ. Adenosine Monophosphate Binding Stabilizes the KTN Domain of the Shewanella denitrificans Kef Potassium Efflux System. Biochemistry 2017; 56:4219-4234. [PMID: 28656748 PMCID: PMC5645763 DOI: 10.1021/acs.biochem.7b00300] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
![]()
Ligand binding is
one of the most fundamental properties of proteins.
Ligand functions fall into three basic types: substrates, regulatory
molecules, and cofactors essential to protein stability, reactivity,
or enzyme–substrate complex formation. The regulation of potassium
ion movement in bacteria is predominantly under the control of regulatory
ligands that gate the relevant channels and transporters, which possess
subunits or domains that contain Rossmann folds (RFs). Here we demonstrate
that adenosine monophosphate (AMP) is bound to both RFs of the dimeric
bacterial Kef potassium efflux system (Kef), where it plays a structural
role. We conclude that AMP binds with high affinity, ensuring that
the site is fully occupied at all times in the cell. Loss of the ability
to bind AMP, we demonstrate, causes protein, and likely dimer, instability
and consequent loss of function. Kef system function is regulated
via the reversible binding of comparatively low-affinity glutathione-based
ligands at the interface between the dimer subunits. We propose this
interfacial binding site is itself stabilized, at least in part, by
AMP binding.
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Affiliation(s)
- Christos Pliotas
- Biomedical Sciences Research Complex, University of St Andrews , North Haugh, St Andrews KY16 9ST, U.K
| | - Samuel C Grayer
- Department of Chemistry, Chemistry Research Laboratory, University of Oxford , Mansfield Road, Oxford OX1 3TA, U.K
| | - Silvia Ekkerman
- Medical Sciences and Nutrition, School of Medicine , Foresterhill, Aberdeen AB25 2ZD, U.K
| | - Anthony K N Chan
- Department of Chemistry, Chemistry Research Laboratory, University of Oxford , Mansfield Road, Oxford OX1 3TA, U.K
| | - Jess Healy
- Department of Chemistry, Chemistry Research Laboratory, University of Oxford , Mansfield Road, Oxford OX1 3TA, U.K
| | - Phedra Marius
- Biomedical Sciences Research Complex, University of St Andrews , North Haugh, St Andrews KY16 9ST, U.K
| | - Wendy Bartlett
- Medical Sciences and Nutrition, School of Medicine , Foresterhill, Aberdeen AB25 2ZD, U.K
| | - Amjad Khan
- Department of Chemistry, Chemistry Research Laboratory, University of Oxford , Mansfield Road, Oxford OX1 3TA, U.K
| | - Wilian A Cortopassi
- Department of Chemistry, Chemistry Research Laboratory, University of Oxford , Mansfield Road, Oxford OX1 3TA, U.K
| | - Shane A Chandler
- Physical & Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford , South Parks Road, Oxford OX1 3QZ, U.K
| | - Tim Rasmussen
- Medical Sciences and Nutrition, School of Medicine , Foresterhill, Aberdeen AB25 2ZD, U.K
| | - Justin L P Benesch
- Physical & Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford , South Parks Road, Oxford OX1 3QZ, U.K
| | - Robert S Paton
- Department of Chemistry, Chemistry Research Laboratory, University of Oxford , Mansfield Road, Oxford OX1 3TA, U.K
| | - Timothy D W Claridge
- Department of Chemistry, Chemistry Research Laboratory, University of Oxford , Mansfield Road, Oxford OX1 3TA, U.K
| | - Samantha Miller
- Medical Sciences and Nutrition, School of Medicine , Foresterhill, Aberdeen AB25 2ZD, U.K
| | - Ian R Booth
- Medical Sciences and Nutrition, School of Medicine , Foresterhill, Aberdeen AB25 2ZD, U.K
| | - James H Naismith
- Biomedical Sciences Research Complex, University of St Andrews , North Haugh, St Andrews KY16 9ST, U.K.,Biotherapy Centre, Sichuan University , Chengdu, China.,RCaH, Rutherford Appleton Laboratory , Harwell Oxford, Didcot OX11 0FA, U.K.,Division of Structural Biology, University of Oxford , Henry Wellcome Building for Genomic Medicine, Old Road Campus, Roosevelt Drive, Headington, Oxford OX3 7BN, U.K
| | - Stuart J Conway
- Department of Chemistry, Chemistry Research Laboratory, University of Oxford , Mansfield Road, Oxford OX1 3TA, U.K.,Freiburg Institute for Advanced Studies-FRIAS, Albert-Ludwigs-Universität Freiburg , Albertstrasse 19, 79104 Freiburg, Germany
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15
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Abstract
Mechanosensitive (MS) ion channels are multimeric integral membrane proteins that respond to increased lipid bilayer tension by opening their nonselective pores to release solutes and relieve increased cytoplasmic pressure. These systems undergo major conformational changes during gating and the elucidation of their mechanism requires a deep understanding of the interplay between lipids and proteins. Lipids are responsible for transmitting lateral tension to MS channels and therefore play a key role in obtaining a molecular-detail model for mechanosensation. Site-directed spin labeling combined with electron paramagnetic resonance (EPR) spectroscopy is a powerful spectroscopic tool in the study of proteins. The main bottleneck for its use relates to challenges associated with successful isolation of the protein of interest, introduction of paramagnetic labels on desired sites, and access to specialized instrumentation and expertise. The design of sophisticated experiments, which combine a variety of existing EPR methodologies to address a diversity of specific questions, require knowledge of the limitations and strengths, characteristic of each particular EPR method. This chapter is using the MS ion channels as paradigms and focuses on the application of different EPR techniques to ion channels, in order to investigate oligomerization, conformation, and the effect of lipids on their regulation. The methodology we followed, from the initial strategic selection of mutants and sample preparation, including protein purification, spin labeling, reconstitution into lipid mimics to the complete set-up of the pulsed-EPR experiments, is described in detail.
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16
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Asadi J, Ferguson S, Raja H, Hacker C, Marius P, Ward R, Pliotas C, Naismith J, Lucocq J. Enhanced imaging of lipid rich nanoparticles embedded in methylcellulose films for transmission electron microscopy using mixtures of heavy metals. Micron 2017; 99:40-48. [PMID: 28419915 PMCID: PMC5465805 DOI: 10.1016/j.micron.2017.03.019] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2017] [Revised: 03/28/2017] [Accepted: 03/29/2017] [Indexed: 02/01/2023]
Abstract
Uranyl acetate/tungsten double stains are proposed for imaging lipid rich nanoparticle in TEM. Combined with methylcellulose embedment, the technique enhances membrane contrast. The technique works for liposomes, nanodiscs and bicelles. The double staining should improve quantification of lipid rich nanoparticles.
Synthetic and naturally occurring lipid-rich nanoparticles are of wide ranging importance in biomedicine. They include liposomes, bicelles, nanodiscs, exosomes and virus particles. The quantitative study of these particles requires methods for high-resolution visualization of the whole population. One powerful imaging method is cryo-EM of vitrified samples, but this is technically demanding, requires specialized equipment, provides low contrast and does not reveal all particles present in a population. Another approach is classical negative stain-EM, which is more accessible but is difficult to standardize for larger lipidic structures, which are prone to artifacts of structure collapse and contrast variability. A third method uses embedment in methylcellulose films containing uranyl acetate as a contrasting agent. Methylcellulose embedment has been widely used for contrasting and supporting cryosections but only sporadically for visualizing lipid rich vesicular structures such as endosomes and exosomes. Here we present a simple methylcellulose-based method for routine and comprehensive visualization of synthetic lipid rich nanoparticles preparations, such as liposomes, bicelles and nanodiscs. It combines a novel double-staining mixture of uranyl acetate (UA) and tungsten-based electron stains (namely phosphotungstic acid (PTA) or sodium silicotungstate (STA)) with methylcellulose embedment. While the methylcellulose supports the delicate lipid structures during drying, the addition of PTA or STA to UA provides significant enhancement in lipid structure display and contrast as compared to UA alone. This double staining method should aid routine structural evaluation and quantification of lipid rich nanoparticles structures.
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Affiliation(s)
- Jalal Asadi
- School of Medicine, University of St Andrews, St. Andrews, Fife, KY16 9TF, UK
| | - Sophie Ferguson
- School of Medicine, University of St Andrews, St. Andrews, Fife, KY16 9TF, UK
| | - Hussain Raja
- School of Medicine, University of St Andrews, St. Andrews, Fife, KY16 9TF, UK
| | - Christian Hacker
- School of Medicine, University of St Andrews, St. Andrews, Fife, KY16 9TF, UK
| | - Phedra Marius
- Biomedical Sciences Research Complex, North Haugh, University of St. Andrews, St. Andrews, Scotland, UK
| | - Richard Ward
- Biomedical Sciences Research Complex, North Haugh, University of St. Andrews, St. Andrews, Scotland, UK
| | - Christos Pliotas
- Biomedical Sciences Research Complex, North Haugh, University of St. Andrews, St. Andrews, Scotland, UK
| | - James Naismith
- Biomedical Sciences Research Complex, North Haugh, University of St. Andrews, St. Andrews, Scotland, UK
| | - John Lucocq
- School of Medicine, University of St Andrews, St. Andrews, Fife, KY16 9TF, UK.
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17
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Pliotas C, Dahl AC, Rasmussen T, Mahendran KR, Smith TK, Marius P, Gault J, Rasmussen A, Robinson CV, Bayley H, Sansom MS, Booth IR, Naismith JH. Gating MscS: structural basis of mechanosensation and the role of lipids in ion channel regulation. Acta Crystallogr A Found Adv 2016. [DOI: 10.1107/s2053273316099459] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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18
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Abstract
Pulse electron paramagnetic resonance (EPR) is gaining increasing importance in structural biology. The PELDOR (pulsed electron–electron double resonance) method allows extracting distance information on the nanometer scale. Here, we demonstrate the efficient extraction of distances from multimeric systems such as membrane‐embedded ion channels where data analysis is commonly hindered by multi‐spin effects.
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Affiliation(s)
- Silvia Valera
- Centre of Magnetic Resonance, University of St Andrews, North Haugh, St Andrews, KY16 9ST, UK.,Biomedical Sciences Research Complex, University of St Andrews, North Haugh, St Andrews, KY16 9ST, UK
| | - Katrin Ackermann
- Centre of Magnetic Resonance, University of St Andrews, North Haugh, St Andrews, KY16 9ST, UK.,Biomedical Sciences Research Complex, University of St Andrews, North Haugh, St Andrews, KY16 9ST, UK
| | - Christos Pliotas
- Centre of Magnetic Resonance, University of St Andrews, North Haugh, St Andrews, KY16 9ST, UK.,Biomedical Sciences Research Complex, University of St Andrews, North Haugh, St Andrews, KY16 9ST, UK
| | - Hexian Huang
- Biomedical Sciences Research Complex, University of St Andrews, North Haugh, St Andrews, KY16 9ST, UK
| | - James H Naismith
- Biomedical Sciences Research Complex, University of St Andrews, North Haugh, St Andrews, KY16 9ST, UK
| | - Bela E Bode
- Centre of Magnetic Resonance, University of St Andrews, North Haugh, St Andrews, KY16 9ST, UK. .,Biomedical Sciences Research Complex, University of St Andrews, North Haugh, St Andrews, KY16 9ST, UK.
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19
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Pliotas C, Dahl ACE, Rasmussen T, Mahendran KR, Smith TK, Marius P, Gault J, Banda T, Rasmussen A, Miller S, Robinson CV, Bayley H, Sansom MSP, Booth IR, Naismith JH. The role of lipids in mechanosensation. Nat Struct Mol Biol 2015; 22:991-8. [PMID: 26551077 PMCID: PMC4675090 DOI: 10.1038/nsmb.3120] [Citation(s) in RCA: 127] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2015] [Accepted: 10/06/2015] [Indexed: 12/13/2022]
Abstract
The ability of proteins to sense membrane tension is pervasive in biology. A higher resolution structure of E. coli MscS, the channel of small conductance, identifies alkyl chains inside pockets formed by the transmembrane helices (TMs). Purified MscS contains E. coli lipids and fluorescence quenching demonstrates that phospholipid acyl chains exchange between bilayer and TM pockets. Molecular dynamics and biophysical analyses show that the volume of the pockets and thus the number of lipid acyl chain within them decreases upon channel opening. Phospholipids with one acyl chain per head group (lysolipids) displace normal phospholipids (two acyl chains) from MscS pockets and trigger channel opening. We propose the extent of acyl chain interdigitation in these pockets determines the conformation of MscS. Where interdigitation is perturbed by increased membrane tension or by lysolipids, the closed state becomes unstable and the channel gates.
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Affiliation(s)
- Christos Pliotas
- Biomedical Sciences Research Complex, University of St. Andrews, St. Andrews, UK
| | | | - Tim Rasmussen
- Institute of Medical Sciences, University of Aberdeen, Aberdeen, UK
| | | | - Terry K Smith
- Biomedical Sciences Research Complex, University of St. Andrews, St. Andrews, UK
| | - Phedra Marius
- Biomedical Sciences Research Complex, University of St. Andrews, St. Andrews, UK
| | - Joseph Gault
- Department of Chemistry, University of Oxford, Oxford, UK
| | - Thandiwe Banda
- Institute of Medical Sciences, University of Aberdeen, Aberdeen, UK
| | - Akiko Rasmussen
- Institute of Medical Sciences, University of Aberdeen, Aberdeen, UK
| | - Samantha Miller
- Institute of Medical Sciences, University of Aberdeen, Aberdeen, UK
| | | | - Hagan Bayley
- Department of Chemistry, University of Oxford, Oxford, UK
| | - Mark S P Sansom
- Department of Biochemistry, University of Oxford, Oxford, UK
| | - Ian R Booth
- Institute of Medical Sciences, University of Aberdeen, Aberdeen, UK.,Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California, USA
| | - James H Naismith
- Biomedical Sciences Research Complex, University of St. Andrews, St. Andrews, UK.,State Key Laboratory of Biotherapy, Sichuan University, Chengdu, China
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20
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Ward R, Pliotas C, Branigan E, Hacker C, Rasmussen A, Hagelueken G, Booth IR, Miller S, Lucocq J, Naismith JH, Schiemann O. Probing the structure of the mechanosensitive channel of small conductance in lipid bilayers with pulsed electron-electron double resonance. Biophys J 2014; 106:834-42. [PMID: 24559986 PMCID: PMC3944623 DOI: 10.1016/j.bpj.2014.01.008] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2013] [Revised: 01/03/2014] [Accepted: 01/07/2014] [Indexed: 01/16/2023] Open
Abstract
Mechanosensitive channel proteins are important safety valves against osmotic shock in bacteria, and are involved in sensing touch and sound waves in higher organisms. The mechanosensitive channel of small conductance (MscS) has been extensively studied. Pulsed electron-electron double resonance (PELDOR or DEER) of detergent-solubilized protein confirms that as seen in the crystal structure, the outer ring of transmembrane helices do not pack against the pore-forming helices, creating an apparent void. The relevance of this void to the functional form of MscS in the bilayer is the subject of debate. Here, we report PELDOR measurements of MscS reconstituted into two lipid bilayer systems: nanodiscs and bicelles. The distance measurements from multiple mutants derived from the PELDOR data are consistent with the detergent-solution arrangement of the protein. We conclude, therefore, that the relative positioning of the transmembrane helices is preserved in mimics of the cell bilayer, and that the apparent voids are not an artifact of detergent solution but a property of the protein that will have to be accounted for in any molecular mechanism of gating.
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Affiliation(s)
- Richard Ward
- Centre for Biomolecular Sciences, University of St. Andrews, St. Andrews, Scotland
| | - Christos Pliotas
- Centre for Biomolecular Sciences, University of St. Andrews, St. Andrews, Scotland
| | - Emma Branigan
- Centre for Biomolecular Sciences, University of St. Andrews, St. Andrews, Scotland
| | - Christian Hacker
- School of Medicine, University of St. Andrews, St. Andrews, Scotland
| | - Akiko Rasmussen
- Institute of Medical Sciences, University of Aberdeen, Aberdeen, Scotland
| | - Gregor Hagelueken
- Institute of Physical and Theoretical Chemistry, University of Bonn, Bonn, Germany
| | - Ian R Booth
- Institute of Medical Sciences, University of Aberdeen, Aberdeen, Scotland
| | - Samantha Miller
- Institute of Medical Sciences, University of Aberdeen, Aberdeen, Scotland
| | - John Lucocq
- School of Medicine, University of St. Andrews, St. Andrews, Scotland
| | - James H Naismith
- Centre for Biomolecular Sciences, University of St. Andrews, St. Andrews, Scotland.
| | - Olav Schiemann
- Institute of Physical and Theoretical Chemistry, University of Bonn, Bonn, Germany; Centre for Biomolecular Sciences, University of St. Andrews, St. Andrews, Scotland.
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21
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Healy J, Ekkerman S, Pliotas C, Richard M, Bartlett W, Grayer SC, Morris GM, Miller S, Booth IR, Conway SJ, Rasmussen T. Understanding the structural requirements for activators of the Kef bacterial potassium efflux system. Biochemistry 2014; 53:1982-92. [PMID: 24601535 PMCID: PMC4004266 DOI: 10.1021/bi5001118] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The potassium efflux system, Kef, protects bacteria against the detrimental effects of electrophilic compounds via acidification of the cytoplasm. Kef is inhibited by glutathione (GSH) but activated by glutathione-S-conjugates (GS-X) formed in the presence of electrophiles. GSH and GS-X bind to overlapping sites on Kef, which are located in a cytosolic regulatory domain. The central paradox of this activation mechanism is that GSH is abundant in cells (at concentrations of ∼10-20 mM), and thus, activating ligands must possess a high differential over GSH in their affinity for Kef. To investigate the structural requirements for binding of a ligand to Kef, a novel fluorescent reporter ligand, S-{[5-(dimethylamino)naphthalen-1-yl]sulfonylaminopropyl} glutathione (DNGSH), was synthesized. By competition assays using DNGSH, complemented by direct binding assays and thermal shift measurements, we show that the well-characterized Kef activator, N-ethylsuccinimido-S-glutathione, has a 10-20-fold higher affinity for Kef than GSH. In contrast, another native ligand that is a poor activator, S-lactoylglutathione, exhibits a similar Kef affinity to GSH. Synthetic ligands were synthesized to contain either rigid or flexible structures and investigated as ligands for Kef. Compounds with rigid structures and high affinity activated Kef. In contrast, flexible ligands with similar binding affinities did not activate Kef. These data provide insight into the structural requirements for Kef gating, paving the way for the development of a screen for potential therapeutic lead compounds targeting the Kef system.
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Affiliation(s)
- Jessica Healy
- Department of Chemistry, Chemistry Research Laboratory, University of Oxford , Mansfield Road, Oxford OX1 3TA, United Kingdom
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Branigan E, Pliotas C, Hagelueken G, Naismith JH. Quantification of free cysteines in membrane and soluble proteins using a fluorescent dye and thermal unfolding. Nat Protoc 2013; 8:2090-7. [PMID: 24091556 DOI: 10.1038/nprot.2013.128] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Cysteine is an extremely useful site for selective attachment of labels to proteins for many applications, including the study of protein structure in solution by electron paramagnetic resonance (EPR), fluorescence spectroscopy and medical imaging. The demand for quantitative data for these applications means that it is important to determine the extent of the cysteine labeling. The efficiency of labeling is sensitive to the 3D context of cysteine within the protein. Where the label or modification is not directly measurable by optical or magnetic spectroscopy, for example, in cysteine modification to dehydroalanine, assessing labeling efficiency is difficult. We describe a simple assay for determining the efficiency of modification of cysteine residues, which is based on an approach previously used to determine membrane protein stability. The assay involves a reaction between the thermally unfolded protein and a thiol-specific coumarin fluorophore that is only fluorescent upon conjugation with thiols. Monitoring fluorescence during thermal denaturation of the protein in the presence of the dye identifies the temperature at which the maximum fluorescence occurs; this temperature differs among proteins. Comparison of the fluorescence intensity at the identified temperature between modified, unmodified (positive control) and cysteine-less protein (negative control) allows for the quantification of free cysteine. We have quantified both site-directed spin labeling and dehydroalanine formation. The method relies on a commonly available fluorescence 96-well plate reader, which rapidly screens numerous samples within 1.5 h and uses <100 μg of material. The approach is robust for both soluble and detergent-solubilized membrane proteins.
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Affiliation(s)
- Emma Branigan
- Biomedical Sciences Research Complex, University of St. Andrews, St. Andrews, UK
| | - Christos Pliotas
- Biomedical Sciences Research Complex, University of St. Andrews, St. Andrews, UK
| | - Gregor Hagelueken
- Biomedical Sciences Research Complex, University of St. Andrews, St. Andrews, UK
| | - James H Naismith
- Biomedical Sciences Research Complex, University of St. Andrews, St. Andrews, UK
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Pliotas C, Ward R, Branigan E, Rasmussen A, Booth IR, Schiemann O, Naismith JH. Measuring Transmembrane Helix Separation on the MscS Mechanosensitive Channel using Pulsed Electron-Electron Double Resonance (PELDOR) Spectroscopy. Biophys J 2013. [DOI: 10.1016/j.bpj.2012.11.2587] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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24
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Rasmussen T, Pliotas C, Lyngberg L, Healy J, Bartlett W, Miller S, Roosild TP, Castronovo S, Conway SJ, Booth IR. Activation and Complex Regulation of the Kef Potassium Efflux System During Protection of Bacteria Against Toxic Electrophiles. Biophys J 2011. [DOI: 10.1016/j.bpj.2010.12.763] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
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