1
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de Jong E, Kocer A. Current Methods for Identifying Plasma Membrane Proteins as Cancer Biomarkers. MEMBRANES 2023; 13:409. [PMID: 37103836 PMCID: PMC10142483 DOI: 10.3390/membranes13040409] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/26/2022] [Revised: 03/31/2023] [Accepted: 04/01/2023] [Indexed: 06/19/2023]
Abstract
Plasma membrane proteins are a special class of biomolecules present on the cellular membrane. They provide the transport of ions, small molecules, and water in response to internal and external signals, define a cell's immunological identity, and facilitate intra- and intercellular communication. Since they are vital to almost all cellular functions, their mutants, or aberrant expression is linked to many diseases, including cancer, where they are a part of cancer cell-specific molecular signatures and phenotypes. In addition, their surface-exposed domains make them exciting biomarkers for targeting by imaging agents and drugs. This review looks at the challenges in identifying cancer-related cell membrane proteins and the current methodologies that solve most of the challenges. We classified the methodologies as biased, i.e., search cells for the presence of already known membrane proteins. Second, we discuss the unbiased methods that can identify proteins without prior knowledge of what they are. Finally, we discuss the potential impact of membrane proteins on the early detection and treatment of cancer.
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2
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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] [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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3
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Pan X, Tran T, Kirsch ZJ, Thompson LK, Vachet RW. Diethylpyrocarbonate-Based Covalent Labeling Mass Spectrometry of Protein Interactions in a Membrane Complex System. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2023; 34:82-91. [PMID: 36475668 PMCID: PMC9812933 DOI: 10.1021/jasms.2c00262] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Membrane-associated proteins are important because they mediate interactions between a cell's external and internal environment and they are often targets of therapeutics. Characterizing their structures and binding interactions, however, is challenging because they typically must be solubilized using artificial membrane systems that can make measurements difficult. Mass spectrometry (MS) is emerging as a valuable tool for studying membrane-associated proteins, and covalent labeling MS has unique potential to provide higher order structure and binding information for these proteins in complicated membrane systems. Here, we demonstrate that diethylpyrocarbonate (DEPC) can be effectively used as a labeling reagent to characterize the binding interactions between a membrane-associated protein and its binding partners in an artificial membrane system. Using chemotaxis histidine kinase (CheA) as a model system, we demonstrate that DEPC-based covalent labeling MS can provide structural and binding information about the ternary complex of CheA with two other proteins that is consistent with structural models of this membrane-associated chemoreceptor system. Despite the moderate hydrophobicity of DEPC, we find that its reactivity with proteins is not substantially influenced by the presence of the artificial membranes. However, correct structural information for this multiprotein chemoreceptor system requires measurements of DEPC labeling at multiple reagent concentrations to enable an accurate comparison between CheA and its ternary complex in the chemoreceptor system. In addition to providing structural information that is consistent with the model of this complex system, the labeling data supplements structural information that is not sufficiently refined in the chemoreceptor model.
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Affiliation(s)
- Xiao Pan
- Department of Chemistry, University of Massachusetts Amherst, Amherst, MA 01003
| | - Thomas Tran
- Molecular and Cellular Biology Program, University of Massachusetts Amherst, Amherst, MA 01003
| | - Zachary J. Kirsch
- Department of Chemistry, University of Massachusetts Amherst, Amherst, MA 01003
| | - Lynmarie K. Thompson
- Department of Chemistry, University of Massachusetts Amherst, Amherst, MA 01003
- Molecular and Cellular Biology Program, University of Massachusetts Amherst, Amherst, MA 01003
| | - Richard W. Vachet
- Department of Chemistry, University of Massachusetts Amherst, Amherst, MA 01003
- Molecular and Cellular Biology Program, University of Massachusetts Amherst, Amherst, MA 01003
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4
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Keener JE, Jayasekera HS, Marty MT. Investigating the Lipid Selectivity of Membrane Proteins in Heterogeneous Nanodiscs. Anal Chem 2022; 94:8497-8505. [PMID: 35621361 DOI: 10.1021/acs.analchem.2c01488] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The structure and function of membrane proteins can be significantly impacted by the surrounding lipid environment, but membrane protein-lipid interactions in lipid bilayers are often difficult to study due to their transient and polydisperse nature. Here, we used two native mass spectrometry (MS) approaches to investigate how the Escherichia coli ammonium transporter trimer (AmtB) and aquaporin Z (AqpZ) selectively remodel their local lipid environment in heterogeneous lipoprotein nanodiscs. First, we used gas-phase ejection to isolate the membrane protein with bound lipids from heterogeneous nanodiscs with different combinations of lipids. Second, we used solution-phase detergent extraction as an orthogonal approach to study membrane protein remodeling of lipids in the nanodisc with native MS. Our results showed that Triton X-100 and lauryldimethylamine oxide retain lipid selectivity that agrees with gas-phase ejection, but C8E4 distorts some preferential lipid interactions. Both approaches reveal that AmtB has a few selective binding sites for phosphatidylcholine (PC) lipids, is selective for binding phosphatidylglycerols (PG) overall, and is nonselective for phosphatidylethanolamines (PE). In contrast, AqpZ prefers either PC or PG over PE and prefers PC over PG. Overall, these experiments provide a picture of how membrane proteins bind different lipid head groups in the context of mixed lipid bilayers.
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Affiliation(s)
- James E Keener
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, United States
| | - Hiruni S Jayasekera
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, United States
| | - Michael T Marty
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, United States.,Bio5 Institute, University of Arizona, Tucson, Arizona 85721, United States
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5
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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] [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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6
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Verteporfin is a Substrate-Selective γ-Secretase Inhibitor that Binds the Amyloid Precursor Protein Transmembrane Domain. J Biol Chem 2022; 298:101792. [PMID: 35247387 PMCID: PMC8968665 DOI: 10.1016/j.jbc.2022.101792] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2021] [Revised: 02/22/2022] [Accepted: 02/26/2022] [Indexed: 11/23/2022] Open
Abstract
This work reports substrate-selective inhibition of a protease with broad substrate specificity based on direct binding of a small molecule inhibitor to the substrate. The target for these studies was γ-secretase protease, which cleaves dozens of different single span membrane protein substrates, including both the C99 domain of the human amyloid precursor protein and the Notch receptor. Substrate-specific inhibition of C99 cleavage is desirable to reduce production of the amyloid-β polypeptide without inhibiting Notch cleavage, a major source of toxicity associated with broad specificity γ-secretase inhibitors. In order to identify a C99-selective inhibitors of the human γ-secretase, we conducted an NMR-based screen of FDA-approved drugs against C99 in model membranes. From this screen, we identified the small molecule verteporfin with these properties. We observed that verteporfin formed a direct 1:1 complex with C99, with a KD of 15-47 μM (depending on the membrane mimetic used), and that it did not bind the transmembrane domain of the Notch-1 receptor. Biochemical assays showed that direct binding of verteporfin to C99 inhibits γ-secretase cleavage of C99 with IC50 values in the range of 15- 164 μM, while Notch-1 cleavage was inhibited only at higher concentrations, and likely via a mechanism that does not involve binding to Notch-1. This work documents a robust NMR-based approach to discovery of small molecule binders to single-span membrane proteins and confirmed that it is possible to inhibit γ-secretase in a substrate-specific manner.
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7
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Higgins AJ, Flynn AJ, Marconnet A, Musgrove LJ, Postis VLG, Lippiat JD, Chung CW, Ceska T, Zoonens M, Sobott F, Muench SP. Cycloalkane-modified amphiphilic polymers provide direct extraction of membrane proteins for CryoEM analysis. Commun Biol 2021; 4:1337. [PMID: 34824357 PMCID: PMC8617058 DOI: 10.1038/s42003-021-02834-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Accepted: 10/27/2021] [Indexed: 12/30/2022] Open
Abstract
Membrane proteins are essential for cellular growth, signalling and homeostasis, making up a large proportion of therapeutic targets. However, the necessity for a solubilising agent to extract them from the membrane creates challenges in their structural and functional study. Although amphipols have been very effective for single-particle electron cryo-microscopy (cryoEM) and mass spectrometry, they rely on initial detergent extraction before exchange into the amphipol environment. Therefore, circumventing this pre-requirement would be a big advantage. Here we use an alternative type of amphipol: a cycloalkane-modified amphiphile polymer (CyclAPol) to extract Escherichia coli AcrB directly from the membrane and demonstrate that the protein can be isolated in a one-step purification with the resultant cryoEM structure achieving 3.2 Å resolution. Together this work shows that cycloalkane amphipols provide a powerful approach for the study of membrane proteins, allowing native extraction and high-resolution structure determination by cryoEM.
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Affiliation(s)
- Anna J Higgins
- School of Biomedical Sciences, Faculty of Biological Sciences & Astbury Centre for Structural and Molecular Biology, University of Leeds, Leeds, LS2 9JT, UK
| | - Alex J Flynn
- School of Biomedical Sciences, Faculty of Biological Sciences & Astbury Centre for Structural and Molecular Biology, University of Leeds, Leeds, LS2 9JT, UK
| | - Anaïs Marconnet
- Université de Paris, Laboratoire de Biologie Physico-Chimique des Protéines Membranaires, CNRS, UMR 7099, F-75005, Paris, France
- Institut de Biologie Physico-Chimique, Fondation Edmond de Rothschild pour le dévelopement de la recherche scientifique, F-75005, Paris, France
| | - Laura J Musgrove
- School of Biomedical Sciences, Faculty of Biological Sciences & Astbury Centre for Structural and Molecular Biology, University of Leeds, Leeds, LS2 9JT, UK
| | - Vincent L G Postis
- School of Biomedical Sciences, Faculty of Biological Sciences & Astbury Centre for Structural and Molecular Biology, University of Leeds, Leeds, LS2 9JT, UK
- Wellcome Centre for Anti-Infectives Research, Drug Discovery Unit, Division of Biological Chemistry and Drug Discovery, University of Dundee, Dundee, DD1 5EH, UK
| | - Jonathan D Lippiat
- School of Biomedical Sciences, Faculty of Biological Sciences & Astbury Centre for Structural and Molecular Biology, University of Leeds, Leeds, LS2 9JT, UK
| | - Chun-Wa Chung
- GlaxoSmithKline, Gunnels Wood Road, Stevenage, SG1 2NY, UK
| | | | - Manuela Zoonens
- Université de Paris, Laboratoire de Biologie Physico-Chimique des Protéines Membranaires, CNRS, UMR 7099, F-75005, Paris, France.
- Institut de Biologie Physico-Chimique, Fondation Edmond de Rothschild pour le dévelopement de la recherche scientifique, F-75005, Paris, France.
| | - Frank Sobott
- School of Molecular and Cellular Biology, Faculty of Biological Sciences & Astbury Centre for Structural and Molecular Biology, University of Leeds, Leeds, LS2 9JT, UK.
| | - Stephen P Muench
- School of Biomedical Sciences, Faculty of Biological Sciences & Astbury Centre for Structural and Molecular Biology, University of Leeds, Leeds, LS2 9JT, UK.
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8
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Kostelic MM, Zak CK, Jayasekera HS, Marty MT. Assembly of Model Membrane Nanodiscs for Native Mass Spectrometry. Anal Chem 2021; 93:5972-5979. [PMID: 33797873 DOI: 10.1021/acs.analchem.1c00735] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Native mass spectrometry (MS) with nanodiscs is a promising technique for characterizing membrane protein and peptide interactions in lipid bilayers. However, prior studies have used nanodiscs made of only one or two lipids, which lack the complexity of a natural lipid bilayer. To better model specific biological membranes, we developed model mammalian, bacterial, and mitochondrial nanodiscs with up to four different phospholipids. Careful selection of lipids with similar masses that balance the fluidity and curvature enabled these complex nanodiscs to be assembled and resolved with native MS. We then applied this approach to characterize the specificity and incorporation of LL-37, a human antimicrobial peptide, in single-lipid nanodiscs versus model bacterial nanodiscs. Overall, development of these model membrane nanodiscs reveals new insights into the assembly of complex nanodiscs and provides a useful toolkit for studying membrane protein, peptide, and lipid interactions in model biological membranes.
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Affiliation(s)
- Marius M Kostelic
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, United States
| | - Ciara K Zak
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, United States
| | - Hiruni S Jayasekera
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, United States
| | - Michael T Marty
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, United States.,Bio5 Institute, University of Arizona, Tucson, Arizona 85721, United States
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9
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Hammerschmid D, van Dyck JF, Sobott F, Calabrese AN. Interrogating Membrane Protein Structure and Lipid Interactions by Native Mass Spectrometry. Methods Mol Biol 2021; 2168:233-261. [PMID: 33582995 DOI: 10.1007/978-1-0716-0724-4_11] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
Abstract
Native mass spectrometry and native ion mobility mass spectrometry are now established techniques in structural biology, with recent work developing these methods for the study of integral membrane proteins reconstituted in both lipid bilayer and detergent environments. Here we show how native mass spectrometry can be used to interrogate integral membrane proteins, providing insights into conformation, oligomerization, subunit composition/stoichiometry, and interactions with detergents/lipids/drugs. Furthermore, we discuss the sample requirements and experimental considerations unique to integral membrane protein native mass spectrometry research.
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Affiliation(s)
- Dietmar Hammerschmid
- Protein Chemistry, Proteomics and Epigenetic Signalling (PPES), Department of Biomedical Sciences, University of Antwerp, Wilrijk, Belgium.,Biomolecular & Analytical Mass Spectrometry Group, Chemistry Department, University of Antwerp, Antwerp, Belgium
| | - Jeroen F van Dyck
- Biomolecular & Analytical Mass Spectrometry Group, Chemistry Department, University of Antwerp, Antwerp, Belgium
| | - Frank Sobott
- Biomolecular & Analytical Mass Spectrometry Group, Chemistry Department, University of Antwerp, Antwerp, Belgium.,Faculty of Biological Sciences, School of Molecular and Cellular Biology, University of Leeds, Leeds, UK.,Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, UK
| | - Antonio N Calabrese
- Faculty of Biological Sciences, School of Molecular and Cellular Biology, University of Leeds, Leeds, UK. .,Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, UK.
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10
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Affiliation(s)
- James E. Keener
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, USA
| | - Guozhi Zhang
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, USA
| | - Michael T. Marty
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, USA
- Bio5 Institute, University of Arizona, Tucson, AZ 85721, USA
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11
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Lau AM, Politis A. Integrative Mass Spectrometry-Based Approaches for Modeling Macromolecular Assemblies. Methods Mol Biol 2021; 2247:221-241. [PMID: 33301120 DOI: 10.1007/978-1-0716-1126-5_12] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Mass spectrometry (MS)-based strategies have emerged as key elements for structural modeling of proteins and their assemblies. In particular, merging together complementary MS tools, through the so-called hybrid approaches, has enabled structural characterization of proteins in their near-native states. Here, we describe how different MS techniques, such as native MS, chemical cross-linking MS, and ion mobility MS, are brought together using sophisticated computational algorithms and modeling restraints. We demonstrate the applicability of the strategy by building accurate models of multimeric protein assemblies. These strategies can practically be applied to any protein complex of interest and be readily integrated with other structural approaches such as electron density maps from cryo-electron microscopy.
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Affiliation(s)
- Andy M Lau
- Department of Chemistry, King's College London, London, UK
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12
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Bagheri Y, Ali AA, You M. Current Methods for Detecting Cell Membrane Transient Interactions. Front Chem 2020; 8:603259. [PMID: 33365301 PMCID: PMC7750205 DOI: 10.3389/fchem.2020.603259] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2020] [Accepted: 10/16/2020] [Indexed: 12/28/2022] Open
Abstract
Short-lived cell membrane complexes play a key role in regulating cell signaling and communication. Many of these complexes are formed based on low-affinity and transient interactions among various lipids and proteins. New techniques have emerged to study these previously overlooked membrane transient interactions. Exciting functions of these transient interactions have been discovered in cellular events such as immune signaling, host-pathogen interactions, and diseases such as cancer. In this review, we have summarized current experimental methods that allow us to detect and analyze short-lived cell membrane protein-protein, lipid-protein, and lipid-lipid interactions. These methods can provide useful information about the strengths, kinetics, and/or spatial patterns of membrane transient interactions. However, each method also has its own limitations. We hope this review can be used as a guideline to help the audience to choose proper approaches for studying membrane transient interactions in different membrane trafficking and cell signaling events.
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Affiliation(s)
| | | | - Mingxu You
- Department of Chemistry, University of Massachusetts, Amherst, MA, United States
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13
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Fantin SM, Huang H, Sanders CR, Ruotolo BT. Collision-Induced Unfolding Differentiates Functional Variants of the KCNQ1 Voltage Sensor Domain. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2020; 31:2348-2355. [PMID: 32960579 PMCID: PMC8106873 DOI: 10.1021/jasms.0c00288] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
The KCNQ1 voltage-gated potassium channel regulates the repolarization of cardiac cells, and a plurality of point mutations in its voltage-sensing domain (VSD) are associated with toxic gain or loss of pore function, resulting in disease. As is the case with many disease-associated membrane proteins, there are hundreds of human variants of interest identified for KCNQ1; however, a significant portion of these variants have not been characterized in relation to their functional and disease associations. Additionally, as the VSD consists of four transmembrane helices, studies into dynamic structural differences among KCNQ1 VSD variants are hindered by the current limitations and deficits in the high-resolution structure determination of membrane proteins. Here, we use native ion mobility-mass spectrometry and collision-induced unfolding (CIU) to address the need for a high throughput-compatible method for the structural characterization of membrane protein variants of unknown significance using the KCNQ1 VSD as a model system. We perform CIU on wild-type and three mutant KCNQ1 VSD forms associated with the toxic gain or loss of function and show through both automated feature detection and comprehensive difference analysis of the CIU data sets that the variants are clearly grouped by function and disease association. We also construct a classification scheme based on the CIU data sets, which is able to differentiate the variant functional groups and classify a recently characterized variant to its correct grouping. Further, we probe the stability of the KCNQ1 VSD variants when liberated from C12E8 micelles at pH 8.0 and find preliminary evidence that the R231C mutation associated with the gain of the pore function is destabilized relative to the wild-type and loss of function variants.
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Affiliation(s)
- Sarah M. Fantin
- University of Michigan Department of Chemistry, Ann Arbor, Michigan 48109, United States
| | - Hui Huang
- Vanderbilt University, Department of Biochemistry, Nashville, Tennessee 37232, United States
| | - Charles R. Sanders
- Vanderbilt University, Department of Biochemistry, Nashville, Tennessee 37232, United States
| | - Brandon T. Ruotolo
- University of Michigan Department of Chemistry, Ann Arbor, Michigan 48109, United States
- Corresponding Author:
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14
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Effects of Detergent on α-Synuclein Structure. A Native MS-Ion Mobility Study. Int J Mol Sci 2020; 21:ijms21217884. [PMID: 33114222 PMCID: PMC7660655 DOI: 10.3390/ijms21217884] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2020] [Revised: 10/16/2020] [Accepted: 10/21/2020] [Indexed: 02/06/2023] Open
Abstract
The intrinsically disordered protein α-synuclein plays a major role in Parkinson’s disease. The protein can oligomerize resulting in the formation of various aggregated species in neuronal cells, leading to neurodegeneration. The interaction of α-synuclein with biological cell membranes plays an important role for specific functions of α-synuclein monomers, e.g., in neurotransmitter release. Using different types of detergents to mimic lipid molecules present in biological membranes, including the presence of Ca2+ ions as an important structural factor, we aimed to gain an understanding of how α-synuclein interacts with membrane models and how this affects the protein conformation and potential oligomerization. We investigated detergent binding stoichiometry, affinity and conformational changes of α-synuclein taking detergent concentration, different detergent structures and charges into account. With native nano-electrospray ionization ion mobility-mass spectrometry, we were able to detect unique conformational patterns resulting from binding of specific detergents to α-synuclein. Our data demonstrate that α-synuclein monomers can interact with detergent molecules irrespective of their charge, that protein-micelle interactions occur and that micelle properties are an important factor.
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15
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Barth M, Schmidt C. Native mass spectrometry-A valuable tool in structural biology. JOURNAL OF MASS SPECTROMETRY : JMS 2020; 55:e4578. [PMID: 32662584 DOI: 10.1002/jms.4578] [Citation(s) in RCA: 38] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2020] [Revised: 05/18/2020] [Accepted: 05/19/2020] [Indexed: 05/16/2023]
Abstract
Proteins and the complexes they form with their ligands are the players of cellular action. Their function is directly linked with their structure making the structural analysis of protein-ligand complexes essential. Classical techniques of structural biology include X-ray crystallography, nuclear magnetic resonance spectroscopy and recently distinguished cryo-electron microscopy. However, protein-ligand complexes are often dynamic and heterogeneous and consequently challenging for these techniques. Alternative approaches are therefore needed and gained importance during the last decades. One alternative is native mass spectrometry, which is the analysis of intact protein complexes in the gas phase. To achieve this, sample preparation and instrument conditions have to be optimised. Native mass spectrometry then reveals stoichiometry, protein interactions and topology of protein assemblies. Advanced techniques such as ion mobility and high-resolution mass spectrometry further add to the range of applications and deliver information on shape and microheterogeneity of the complexes. In this tutorial, we explain the basics of native mass spectrometry including sample requirements, instrument modifications and interpretation of native mass spectra. We further discuss the developments of native mass spectrometry and provide example spectra and applications.
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Affiliation(s)
- Marie Barth
- Interdisciplinary Research Center HALOmem, Charles Tanford Protein Center, Institute for Biochemistry and Biotechnology, Martin Luther University Halle-Wittenberg, Halle, Germany
| | - Carla Schmidt
- Interdisciplinary Research Center HALOmem, Charles Tanford Protein Center, Institute for Biochemistry and Biotechnology, Martin Luther University Halle-Wittenberg, Halle, Germany
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16
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Structural predictions of the functions of membrane proteins from HDX-MS. Biochem Soc Trans 2020; 48:971-979. [PMID: 32597490 PMCID: PMC7329338 DOI: 10.1042/bst20190880] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2020] [Revised: 06/02/2020] [Accepted: 06/04/2020] [Indexed: 11/17/2022]
Abstract
HDX-MS has emerged as a powerful tool to interrogate the structure and dynamics of proteins and their complexes. Recent advances in the methodology and instrumentation have enabled the application of HDX-MS to membrane proteins. Such targets are challenging to investigate with conventional strategies. Developing new tools are therefore pertinent for improving our fundamental knowledge of how membrane proteins function in the cell. Importantly, investigating this central class of biomolecules within their native lipid environment remains a challenge but also a key goal ahead. In this short review, we outline recent progresses in dissecting the conformational mechanisms of membrane proteins using HDX-MS. We further describe how the use of computational strategies can aid the interpretation of experimental data and enable visualisation of otherwise intractable membrane protein states. This unique integration of experiments with computations holds significant potential for future applications.
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17
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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] [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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18
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Exploring the structure and dynamics of macromolecular complexes by native mass spectrometry. J Proteomics 2020; 222:103799. [DOI: 10.1016/j.jprot.2020.103799] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2019] [Revised: 03/23/2020] [Accepted: 04/25/2020] [Indexed: 12/15/2022]
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19
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Bender J, Schmidt C. Mass spectrometry of membrane protein complexes. Biol Chem 2020; 400:813-829. [PMID: 30956223 DOI: 10.1515/hsz-2018-0443] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2018] [Accepted: 02/25/2019] [Indexed: 12/24/2022]
Abstract
Membrane proteins are key players in the cell. Due to their hydrophobic nature they require solubilising agents such as detergents or membrane mimetics during purification and, consequently, are challenging targets in structural biology. In addition, their natural lipid environment is crucial for their structure and function further hampering their analysis. Alternative approaches are therefore required when the analysis by conventional techniques proves difficult. In this review, we highlight the broad application of mass spectrometry (MS) for the characterisation of membrane proteins and their interactions with lipids. We show that MS unambiguously identifies the protein and lipid components of membrane protein complexes, unravels their three-dimensional arrangements and further provides clues of protein-lipid interactions.
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Affiliation(s)
- Julian Bender
- Interdisciplinary Research Center HALOmem, Charles Tanford Protein Centre, Martin Luther University Halle-Wittenberg, Institute for Biochemistry and Biotechnology, Kurt-Mothes-Str. 3a, D-06120 Halle, Germany
| | - Carla Schmidt
- Interdisciplinary Research Center HALOmem, Charles Tanford Protein Centre, Martin Luther University Halle-Wittenberg, Institute for Biochemistry and Biotechnology, Kurt-Mothes-Str. 3a, D-06120 Halle, Germany
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20
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Fantin SM, Parson KF, Niu S, Liu J, Polasky DA, Dixit SM, Ferguson-Miller SM, Ruotolo BT. Collision Induced Unfolding Classifies Ligands Bound to the Integral Membrane Translocator Protein. Anal Chem 2019; 91:15469-15476. [PMID: 31743004 DOI: 10.1021/acs.analchem.9b03208] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Membrane proteins represent most current therapeutic targets, yet remain understudied due to their insolubility in aqueous solvents and generally low yields during purification and expression. Ion mobility-mass spectrometry and collision induced unfolding experiments have recently garnered attention as methods capable of directly detecting and quantifying ligand binding within a wide range of membrane protein systems. Despite prior success, ionized surfactant often creates chemical noise patterns resulting in significant challenges surrounding the study of small membrane protein-ligand complexes. Here, we present a new data analysis workflow that overcomes such chemical noise and then utilize this approach to quantify and classify ligand binding associated with the 36 kDa dimer of translocator protein (TSPO). Following our denoising protocol, we detect separate gas-phase unfolding signatures for lipid and protoporphyrin TSPO binders, molecular classes that likely interact with separate regions of the protein surface. Further, a detailed classification analysis reveals that lipid alkyl chain saturation levels can be detected within our gas-phase protein unfolding data. We combine these data and classification schemes with mass spectra acquired directly from liquid-liquid extracts to propose an identity for a previously unknown endogenous TSPO ligand.
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Affiliation(s)
- Sarah M Fantin
- Department of Chemistry , University of Michigan , Ann Arbor , Michigan 48109 , United States
| | - Kristine F Parson
- Department of Chemistry , University of Michigan , Ann Arbor , Michigan 48109 , United States
| | - Shuai Niu
- Department of Chemistry , University of Michigan , Ann Arbor , Michigan 48109 , United States
| | - Jian Liu
- Department of Biochemistry and Molecular Biology , Michigan State University , East Lansing , Michigan 48824 , United States
| | - Daniel A Polasky
- Department of Chemistry , University of Michigan , Ann Arbor , Michigan 48109 , United States
| | - Sugyan M Dixit
- Department of Chemistry , University of Michigan , Ann Arbor , Michigan 48109 , United States
| | - Shelagh M Ferguson-Miller
- Department of Biochemistry and Molecular Biology , Michigan State University , East Lansing , Michigan 48824 , United States
| | - Brandon T Ruotolo
- Department of Chemistry , University of Michigan , Ann Arbor , Michigan 48109 , United States
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21
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Martens C, Shekhar M, Lau AM, Tajkhorshid E, Politis A. Integrating hydrogen-deuterium exchange mass spectrometry with molecular dynamics simulations to probe lipid-modulated conformational changes in membrane proteins. Nat Protoc 2019; 14:3183-3204. [PMID: 31605097 PMCID: PMC7058097 DOI: 10.1038/s41596-019-0219-6] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2019] [Accepted: 06/20/2019] [Indexed: 12/20/2022]
Abstract
Biological membranes define the boundaries of cells and are composed primarily of phospholipids and membrane proteins. It has become increasingly evident that direct interactions of membrane proteins with their surrounding lipids play key roles in regulating both protein conformations and function. However, the exact nature and structural consequences of these interactions remain difficult to track at the molecular level. Here, we present a protocol that specifically addresses this challenge. First, hydrogen-deuterium exchange mass spectrometry (HDX-MS) of membrane proteins incorporated into nanodiscs of controlled lipid composition is used to obtain information on the lipid species that are involved in modulating the conformational changes in the membrane protein. Then molecular dynamics (MD) simulations in lipid bilayers are used to pinpoint likely lipid-protein interactions, which can be tested experimentally using HDX-MS. By bringing together the MD predictions with the conformational readouts from HDX-MS, we have uncovered key lipid-protein interactions implicated in stabilizing important functional conformations. This protocol can be applied to virtually any integral membrane protein amenable to classic biophysical studies and for which a near-atomic-resolution structure or homology model is available. This protocol takes ~4 d to complete, excluding the time for data analysis and MD simulations, which depends on the size of the protein under investigation.
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Affiliation(s)
- Chloe Martens
- Department of Chemistry, King's College London, London, UK
- Department of Chemistry, Center for Structural Biology and Bioinformatics, Université Libre de Bruxelles, Brussels, Belgium
| | - Mrinal Shekhar
- Center for Biophysics and Quantitative Biology, Department of Biochemistry, NIH Center for Macromolecular Modeling and Bioinformatics, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Andy M Lau
- Department of Chemistry, King's College London, London, UK
| | - Emad Tajkhorshid
- Center for Biophysics and Quantitative Biology, Department of Biochemistry, NIH Center for Macromolecular Modeling and Bioinformatics, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
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22
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Österlund N, Moons R, Ilag LL, Sobott F, Gräslund A. Native Ion Mobility-Mass Spectrometry Reveals the Formation of β-Barrel Shaped Amyloid-β Hexamers in a Membrane-Mimicking Environment. J Am Chem Soc 2019; 141:10440-10450. [DOI: 10.1021/jacs.9b04596] [Citation(s) in RCA: 63] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Nicklas Österlund
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden
| | - Rani Moons
- Department of Chemistry, University of Antwerp, Antwerp, Belgium
| | - Leopold L. Ilag
- Department of Environmental Science and Analytical Chemistry, Stockholm University, Stockholm, Sweden
| | - Frank Sobott
- Department of Chemistry, University of Antwerp, Antwerp, Belgium
- The Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, The United Kingdom
- School of Molecular and Cellular Biology, University of Leeds, Leeds, The United Kingdom
| | - Astrid Gräslund
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden
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23
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Ahdash Z, Lau AM, Martens C, Politis A. Analyzing Protein Architectures and Protein-Ligand Complexes by Integrative Structural Mass Spectrometry. J Vis Exp 2018. [PMID: 30371663 PMCID: PMC6235531 DOI: 10.3791/57966] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Proteins are an important class of biological macromolecules that play many key roles in cellular functions including gene expression, catalyzing metabolic reactions, DNA repair and replication. Therefore, a detailed understanding of these processes provides critical information on how cells function. Integrative structural MS methods offer structural and dynamical information on protein complex assembly, complex connectivity, subunit stoichiometry, protein oligomerization and ligand binding. Recent advances in integrative structural MS have allowed for the characterization of challenging biological systems including large DNA binding proteins and membrane proteins. This protocol describes how to integrate diverse MS data such as native MS and ion mobility-mass spectrometry (IM-MS) with molecular dynamics simulations to gain insights into a helicase-nuclease DNA repair protein complex. The resulting approach provides a framework for detailed studies of ligand binding to other protein complexes involved in important biological processes.
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Affiliation(s)
| | - Andy M Lau
- Department of Chemistry, King's College London
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24
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Calabrese AN, Radford SE. Mass spectrometry-enabled structural biology of membrane proteins. Methods 2018; 147:187-205. [DOI: 10.1016/j.ymeth.2018.02.020] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2017] [Revised: 01/30/2018] [Accepted: 02/21/2018] [Indexed: 01/01/2023] Open
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25
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Liu P, Zhao Y, Liu X, Sun J, Xu D, Li Y, Li Q, Wang L, Yang S, Fan C, Lin J. Charge Neutralization Drives the Shape Reconfiguration of DNA Nanotubes. Angew Chem Int Ed Engl 2018; 57:5418-5422. [PMID: 29528530 PMCID: PMC6142180 DOI: 10.1002/anie.201801498] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2018] [Indexed: 12/29/2022]
Abstract
Reconfiguration of membrane protein channels for gated transport is highly regulated under physiological conditions. However, a mechanistic understanding of such channels remains challenging owing to the difficulty in probing subtle gating-associated structural changes. Herein, we show that charge neutralization can drive the shape reconfiguration of a biomimetic 6-helix bundle DNA nanotube (6HB). Specifically, 6HB adopts a compact state when its charge is neutralized by Mg2+ ; whereas Na+ switches it to the expanded state, as revealed by MD simulations, small-angle X-ray scattering (SAXS), and FRET characterization. Furthermore, partial neutralization of the DNA backbone charges by chemical modification renders 6HB compact and insensitive to ions, suggesting an interplay between electrostatic and hydrophobic forces in the channels. This system provides a platform for understanding the structure-function relationship of biological channels and designing rules for the shape control of DNA nanostructures in biomedical applications.
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Affiliation(s)
- Pi Liu
- State Key Laboratory of Medicinal Chemical Biology, College of Pharmacy and Tianjin Key Laboratory of Molecular Drug Research, Nankai University Tianjin 300353 (China); Biodesign Center, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences Tianjin 300308 (China)
| | - Yan Zhao
- Division of Physical Biology & Bioimaging Center, Shanghai Synchrotron Radiation Facility, CAS Key Laboratory of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences Shanghai 201800 (China)
| | - Xiaoguo Liu
- Division of Physical Biology & Bioimaging Center, Shanghai Synchrotron Radiation Facility, CAS Key Laboratory of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences Shanghai 201800 (China)
| | - Jixue Sun
- State Key Laboratory of Medicinal Chemical Biology, College of Pharmacy and Tianjin Key Laboratory of Molecular Drug Research, Nankai University Tianjin 300353 (China)
| | - Dede Xu
- State Key Laboratory of Medicinal Chemical Biology, College of Pharmacy and Tianjin Key Laboratory of Molecular Drug Research, Nankai University Tianjin 300353 (China)
| | - Yang Li
- State Key Laboratory of Medicinal Chemical Biology, College of Pharmacy and Tianjin Key Laboratory of Molecular Drug Research, Nankai University Tianjin 300353 (China)
| | - Qian Li
- Division of Physical Biology & Bioimaging Center, Shanghai Synchrotron Radiation Facility, CAS Key Laboratory of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences Shanghai 201800 (China)
| | - Lihua Wang
- Division of Physical Biology & Bioimaging Center, Shanghai Synchrotron Radiation Facility, CAS Key Laboratory of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences Shanghai 201800 (China)
| | - Sichun Yang
- Center for Proteomics and Department of Nutrition Case Western Reserve University 10900 Euclid Ave, Cleveland, OH 44106-4988 (USA)
| | - Chunhai Fan
- Division of Physical Biology & Bioimaging Center, Shanghai Synchrotron Radiation Facility, CAS Key Laboratory of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences Shanghai 201800 (China)
| | - Jianping Lin
- State Key Laboratory of Medicinal Chemical Biology, College of Pharmacy and Tianjin Key Laboratory of Molecular Drug Research, Nankai University Tianjin 300353 (China); Biodesign Center, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences Tianjin 300308 (China)
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26
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Gupta K, Li J, Liko I, Gault J, Bechara C, Wu D, Hopper JTS, Giles K, Benesch JLP, Robinson CV. Identifying key membrane protein lipid interactions using mass spectrometry. Nat Protoc 2018; 13:1106-1120. [PMID: 29700483 PMCID: PMC6049616 DOI: 10.1038/nprot.2018.014] [Citation(s) in RCA: 68] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
With the recent success in determining membrane protein structures, further detailed understanding of the identity and function of the bound lipidome is essential. Using an approach that combines high-energy native mass spectrometry (HE-nMS) and solution-phase lipid profiling, this protocol can be used to determine the identity of the endogenous lipids that directly interact with a protein. Furthermore, this method can identify systems in which such lipid binding has a major role in regulating the oligomeric assembly of membrane proteins. The protocol begins with recording of the native mass spectrum of the protein of interest, under successive delipidation conditions, to determine whether delipidation leads to disruption of the oligomeric state. Subsequently, we propose using a bipronged strategy: first, an HE-nMS platform is used that allows dissociation of the detergent micelle at the front end of the instrument. This allows for isolation of the protein-lipid complex at the quadrupole and successive fragmentation at the collision cell, which leads to identification of the bound lipid masses. Next, simultaneous coupling of this with in-solution LC-MS/MS-based identification of extracted lipids reveals the complete identity of the interacting lipidome that copurifies with the proteins. Assimilation of the results of these two sets of experiments divulges the complete identity of the set of lipids that directly interact with the membrane protein of interest, and can further delineate its role in maintaining the oligomeric state of the protein. The entire procedure takes 2 d to complete.
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Affiliation(s)
- Kallol Gupta
- Department of Chemistry, University of Oxford, Oxford, UK
| | - Jingwen Li
- Department of Chemistry, University of Oxford, Oxford, UK
| | - Idlir Liko
- Department of Chemistry, University of Oxford, Oxford, UK
| | - Joseph Gault
- Department of Chemistry, University of Oxford, Oxford, UK
| | - Cherine Bechara
- Department of Chemistry, University of Oxford, Oxford, UK
- Institut de Genomique Fonctionnelle, CNRS UMR-5203, INSERM U1191, University of Montpellier, Montpellier, France
| | - Di Wu
- Department of Chemistry, University of Oxford, Oxford, UK
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27
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Structural Lipids Enable the Formation of Functional Oligomers of the Eukaryotic Purine Symporter UapA. Cell Chem Biol 2018; 25:840-848.e4. [PMID: 29681524 PMCID: PMC6058078 DOI: 10.1016/j.chembiol.2018.03.011] [Citation(s) in RCA: 54] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2017] [Revised: 02/27/2018] [Accepted: 03/22/2018] [Indexed: 11/25/2022]
Abstract
The role of membrane lipids in modulating eukaryotic transporter assembly and function remains unclear. We investigated the effect of membrane lipids in the structure and transport activity of the purine transporter UapA from Aspergillus nidulans. We found that UapA exists mainly as a dimer and that two lipid molecules bind per UapA dimer. We identified three phospholipid classes that co-purified with UapA: phosphatidylcholine, phosphatidylethanolamine (PE), and phosphatidylinositol (PI). UapA delipidation caused dissociation of the dimer into monomers. Subsequent addition of PI or PE rescued the UapA dimer and allowed recovery of bound lipids, suggesting a central role of these lipids in stabilizing the dimer. Molecular dynamics simulations predicted a lipid binding site near the UapA dimer interface. Mutational analyses established that lipid binding at this site is essential for formation of functional UapA dimers. We propose that structural lipids have a central role in the formation of functional, dimeric UapA. Mass spectrometry reveals specific lipid binding to the eukaryotic transporter UapA Interfacial lipids stabilize the functional UapA dimer MD simulations reveal the lipid binding sites Mutagenesis of a lipid binding site disrupts UapA dimerization and function in vivo
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28
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Liu P, Zhao Y, Liu X, Sun J, Xu D, Li Y, Li Q, Wang L, Yang S, Fan C, Lin J. Charge Neutralization Drives the Shape Reconfiguration of DNA Nanotubes. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201801498] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- Pi Liu
- State Key Laboratory of Medicinal Chemical Biology, College of Pharmacy and Tianjin Key Laboratory of Molecular Drug Research; Nankai University; Tianjin 300353 China
- Biodesign Center, Tianjin Institute of Industrial Biotechnology; Chinese Academy of Sciences; Tianjin 300308 China
| | - Yan Zhao
- Division of Physical Biology & Bioimaging Center, Shanghai Synchrotron Radiation Facility, CAS Key Laboratory of Interfacial Physics and Technology; Shanghai Institute of Applied Physics, Chinese Academy of Sciences; Shanghai 201800 China
| | - Xiaoguo Liu
- Division of Physical Biology & Bioimaging Center, Shanghai Synchrotron Radiation Facility, CAS Key Laboratory of Interfacial Physics and Technology; Shanghai Institute of Applied Physics, Chinese Academy of Sciences; Shanghai 201800 China
| | - Jixue Sun
- State Key Laboratory of Medicinal Chemical Biology, College of Pharmacy and Tianjin Key Laboratory of Molecular Drug Research; Nankai University; Tianjin 300353 China
| | - Dede Xu
- State Key Laboratory of Medicinal Chemical Biology, College of Pharmacy and Tianjin Key Laboratory of Molecular Drug Research; Nankai University; Tianjin 300353 China
| | - Yang Li
- State Key Laboratory of Medicinal Chemical Biology, College of Pharmacy and Tianjin Key Laboratory of Molecular Drug Research; Nankai University; Tianjin 300353 China
| | - Qian Li
- Division of Physical Biology & Bioimaging Center, Shanghai Synchrotron Radiation Facility, CAS Key Laboratory of Interfacial Physics and Technology; Shanghai Institute of Applied Physics, Chinese Academy of Sciences; Shanghai 201800 China
| | - Lihua Wang
- Division of Physical Biology & Bioimaging Center, Shanghai Synchrotron Radiation Facility, CAS Key Laboratory of Interfacial Physics and Technology; Shanghai Institute of Applied Physics, Chinese Academy of Sciences; Shanghai 201800 China
| | - Sichun Yang
- Center for Proteomics and Department of Nutrition; Case Western Reserve University; 10900 Euclid Ave Cleveland OH 44106-4988 USA
| | - Chunhai Fan
- Division of Physical Biology & Bioimaging Center, Shanghai Synchrotron Radiation Facility, CAS Key Laboratory of Interfacial Physics and Technology; Shanghai Institute of Applied Physics, Chinese Academy of Sciences; Shanghai 201800 China
| | - Jianping Lin
- State Key Laboratory of Medicinal Chemical Biology, College of Pharmacy and Tianjin Key Laboratory of Molecular Drug Research; Nankai University; Tianjin 300353 China
- Biodesign Center, Tianjin Institute of Industrial Biotechnology; Chinese Academy of Sciences; Tianjin 300308 China
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29
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Lipids Shape the Electron Acceptor-Binding Site of the Peripheral Membrane Protein Dihydroorotate Dehydrogenase. Cell Chem Biol 2018; 25:309-317.e4. [PMID: 29358052 PMCID: PMC5856493 DOI: 10.1016/j.chembiol.2017.12.012] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2017] [Revised: 11/21/2017] [Accepted: 12/20/2017] [Indexed: 11/23/2022]
Abstract
The interactions between proteins and biological membranes are important for drug development, but remain notoriously refractory to structural investigation. We combine non-denaturing mass spectrometry (MS) with molecular dynamics (MD) simulations to unravel the connections among co-factor, lipid, and inhibitor binding in the peripheral membrane protein dihydroorotate dehydrogenase (DHODH), a key anticancer target. Interrogation of intact DHODH complexes by MS reveals that phospholipids bind via their charged head groups at a limited number of sites, while binding of the inhibitor brequinar involves simultaneous association with detergent molecules. MD simulations show that lipids support flexible segments in the membrane-binding domain and position the inhibitor and electron acceptor-binding site away from the membrane surface, similar to the electron acceptor-binding site in respiratory chain complex I. By complementing MS with MD simulations, we demonstrate how a peripheral membrane protein uses lipids to modulate its structure in a similar manner as integral membrane proteins. Mass spectrometry captures intact complexes of the peripheral membrane protein DHODH Detergent removal in the gas phase reveals lipid and co-factor binding DHODH attaches to the membrane by binding charged phospholipids Lipids stabilize the flexible substrate- and drug-binding site
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30
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Bavi N, Martinac AD, Cortes DM, Bavi O, Ridone P, Nomura T, Hill AP, Martinac B, Perozo E. Structural Dynamics of the MscL C-terminal Domain. Sci Rep 2017; 7:17229. [PMID: 29222414 PMCID: PMC5722894 DOI: 10.1038/s41598-017-17396-w] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Accepted: 11/16/2017] [Indexed: 12/17/2022] Open
Abstract
The large conductance mechanosensitive channel (MscL), acts as an osmoprotective emergency valve in bacteria by opening a large, water-filled pore in response to changes in membrane tension. In its closed configuration, the last 36 residues at the C-terminus form a bundle of five α-helices co-linear with the five-fold axis of symmetry. Here, we examined the structural dynamics of the C-terminus of EcMscL using site-directed spin labelling electron paramagnetic resonance (SDSL EPR) spectroscopy. These experiments were complemented with computational modelling including molecular dynamics (MD) simulations and finite element (FE) modelling. Our results show that under physiological conditions, the C-terminus is indeed an α-helical bundle, located near the five-fold symmetry axis of the molecule. Both experiments and computational modelling demonstrate that only the top part of the C-terminal domain (from the residue A110 to E118) dissociates during the channel gating, while the rest of the C-terminus stays assembled. This result is consistent with the view that the C-terminus functions as a molecular sieve and stabilizer of the oligomeric MscL structure as previously suggested.
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Affiliation(s)
- Navid Bavi
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, New South Wales, 2010, Australia
- St. Vincent's Clinical School, The University of New South Wales, Darlinghurst (Sydney), New South Wales, 2010, Australia
| | - Adam D Martinac
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, New South Wales, 2010, Australia
- School of Mechanical & Mining Engineering, University of Queensland, St. Lucia (Brisbane), QLD 4072, Brisbane, Australia
| | - D Marien Cortes
- Texas Tech University Health Sciences Center, Lubbock, Texas, 79430, USA
| | - Omid Bavi
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, New South Wales, 2010, Australia
- Department of Physics, University of Tehran, Tehran, 1439955961, Iran
| | - Pietro Ridone
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, New South Wales, 2010, Australia
- St. Vincent's Clinical School, The University of New South Wales, Darlinghurst (Sydney), New South Wales, 2010, Australia
| | - Takeshi Nomura
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, New South Wales, 2010, Australia
- Department of Rehabilitation, Kyushu Nutrition Welfare University, Kitakyushu, 800-029, Japan
| | - Adam P Hill
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, New South Wales, 2010, Australia
- St. Vincent's Clinical School, The University of New South Wales, Darlinghurst (Sydney), New South Wales, 2010, Australia
| | - Boris Martinac
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, New South Wales, 2010, Australia.
- St. Vincent's Clinical School, The University of New South Wales, Darlinghurst (Sydney), New South Wales, 2010, Australia.
| | - Eduardo Perozo
- Department of Biochemistry and Molecular Biology, University of Chicago, 929 E 57th St, Chicago, Illinois, 60637, USA.
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Shrivastav V, Nahin M, Hogan CJ, Larriba-Andaluz C. Benchmark Comparison for a Multi-Processing Ion Mobility Calculator in the Free Molecular Regime. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2017; 28:1540-1551. [PMID: 28477243 DOI: 10.1007/s13361-017-1661-8] [Citation(s) in RCA: 75] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2016] [Revised: 03/08/2017] [Accepted: 03/14/2017] [Indexed: 06/07/2023]
Abstract
A benchmark comparison between two ion mobility and collision cross-section (CCS) calculators, MOBCAL and IMoS, is presented here as a standard to test the efficiency and performance of both programs. Utilizing 47 organic ions, results are in excellent agreement between IMoS and MOBCAL in He and N2, when both programs use identical input parameters. Due to a more efficiently written algorithm and to its parallelization, IMoS is able to calculate the same CCS (within 1%) with a speed around two orders of magnitude faster than its MOBCAL counterpart when seven cores are used. Due to the high computational cost of MOBCAL in N2, reaching tens of thousands of seconds even for small ions, the comparison between IMoS and MOBCAL is stopped at 70 atoms. Large biomolecules (>10000 atoms) remain computationally expensive when IMoS is used in N2 (even when employing 16 cores). Approximations such as diffuse trajectory methods (DHSS, TDHSS) with and without partial charges and projected area approximation corrections can be used to reduce the total computational time by several folds without hurting the accuracy of the solution. These latter methods can in principle be used with coarse-grained model structures and should yield acceptable CCS results. Graphical Abstract ᅟ.
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Affiliation(s)
- Vaibhav Shrivastav
- Department of Mechanical Engineering, IUPUI, Indianapolis, IN, 46202, USA
| | - Minal Nahin
- Department of Mechanical Engineering, IUPUI, Indianapolis, IN, 46202, USA
| | - Christopher J Hogan
- Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN, 55455, USA
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32
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Liu Y, Cong X, Liu W, Laganowsky A. Characterization of Membrane Protein-Lipid Interactions by Mass Spectrometry Ion Mobility Mass Spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2017; 28:579-586. [PMID: 27924494 DOI: 10.1007/s13361-016-1555-1] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2016] [Revised: 10/06/2016] [Accepted: 11/03/2016] [Indexed: 05/21/2023]
Abstract
Lipids in the biological membrane can modulate the structure and function of integral and peripheral membrane proteins. Distinguishing individual lipids that bind selectively to membrane protein complexes from an ensemble of lipid-bound species remains a daunting task. Recently, ion mobility mass spectrometry (IM-MS) has proven to be invaluable for interrogating the interactions between protein and individual lipids, where the complex undergoes collision induced unfolding followed by quantification of the unfolding pathway to assess the effect of these interactions. However, gas-phase unfolding experiments for membrane proteins are typically performed on the entire ensemble (apo and lipid bound species), raising uncertainty to the contribution of individual lipids and the species that are ejected in the unfolding process. Here, we describe the application of mass spectrometry ion mobility mass spectrometry (MS-IM-MS) for isolating ions corresponding to lipid-bound states of a model integral membrane protein, ammonia channel (AmtB) from Escherichia coli. Free of ensemble effects, MS-IM-MS reveals that bound lipids are ejected as neutral species; however, no correlation was found between the lipid-induced stabilization of complex and their equilibrium binding constants. In comparison to data obtained by IM-MS, there are surprisingly limited differences in stability measurements from IM-MS and MS-IM-MS. The approach described here to isolate ions of membrane protein complexes will be useful for other MS methods, such as surface induced dissociation or collision induced dissociation to determine the stoichiometry of hetero-oligomeric membrane protein complexes. Graphical Abstract ᅟ.
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Affiliation(s)
- Yang Liu
- Center for Infectious and Inflammatory Diseases, Institute of Biosciences and Technology, Texas A&M University, Houston, TX, 77030, USA
| | - Xiao Cong
- Center for Infectious and Inflammatory Diseases, Institute of Biosciences and Technology, Texas A&M University, Houston, TX, 77030, USA
| | - Wen Liu
- Center for Infectious and Inflammatory Diseases, Institute of Biosciences and Technology, Texas A&M University, Houston, TX, 77030, USA
| | - Arthur Laganowsky
- Center for Infectious and Inflammatory Diseases, Institute of Biosciences and Technology, Texas A&M University, Houston, TX, 77030, USA.
- Department of Chemistry, Texas A&M University, College Station, TX, 77842, USA.
- Department of Microbial Pathogenesis and Immunology, College of Medicine, Texas A&M University, Bryan, TX, 77807, USA.
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Li J, Lyu W, Rossetti G, Konijnenberg A, Natalello A, Ippoliti E, Orozco M, Sobott F, Grandori R, Carloni P. Proton Dynamics in Protein Mass Spectrometry. J Phys Chem Lett 2017; 8:1105-1112. [PMID: 28207277 DOI: 10.1021/acs.jpclett.7b00127] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Native electrospray ionization/ion mobility-mass spectrometry (ESI/IM-MS) allows an accurate determination of low-resolution structural features of proteins. Yet, the presence of proton dynamics, observed already by us for DNA in the gas phase, and its impact on protein structural determinants, have not been investigated so far. Here, we address this issue by a multistep simulation strategy on a pharmacologically relevant peptide, the N-terminal residues of amyloid-β peptide (Aβ(1-16)). Our calculations reproduce the experimental maximum charge state from ESI-MS and are also in fair agreement with collision cross section (CCS) data measured here by ESI/IM-MS. Although the main structural features are preserved, subtle conformational changes do take place in the first ∼0.1 ms of dynamics. In addition, intramolecular proton dynamics processes occur on the picosecond-time scale in the gas phase as emerging from quantum mechanics/molecular mechanics (QM/MM) simulations at the B3LYP level of theory. We conclude that proton transfer phenomena do occur frequently during fly time in ESI-MS experiments (typically on the millisecond time scale). However, the structural changes associated with the process do not significantly affect the structural determinants.
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Affiliation(s)
- Jinyu Li
- College of Chemistry, Fuzhou University , 350002 Fuzhou, China
| | - Wenping Lyu
- Computational Biomedicine, Institute for Advanced Simulation IAS-5 and Institute of Neuroscience and Medicine INM-9, Forschungszentrum Jülich , 52425 Jülich, Germany
- Faculty of Mathematics, Computer Science and Natural Sciences, RWTH-Aachen University , 52056 Aachen, Germany
- Computation-Based Science and Technology Research Center, Cyprus Institute , 2121 Aglantzia, Nicosia, Cyprus
| | - Giulia Rossetti
- Computational Biomedicine, Institute for Advanced Simulation IAS-5 and Institute of Neuroscience and Medicine INM-9, Forschungszentrum Jülich , 52425 Jülich, Germany
- Department of Hematology, Oncology, Hemostaseology, and Stem Cell Transplantation, Faculty of Medicine, RWTH Aachen University , 52062 Aachen, Germany
- Jülich Supercomputing Centre (JSC), Forschungszentrum Jülich , D-52425 Jülich, Germany
| | - Albert Konijnenberg
- Biomolecular & Analytical Mass Spectrometry group, Department of Chemistry, University of Antwerp , 2000 Antwerpen, Belgium
| | - Antonino Natalello
- Department of Biotechnology and Biosciences, University of Milano-Bicocca , Piazza della Scienza 2, 20126 Milan, Italy
| | - Emiliano Ippoliti
- Computational Biomedicine, Institute for Advanced Simulation IAS-5 and Institute of Neuroscience and Medicine INM-9, Forschungszentrum Jülich , 52425 Jülich, Germany
| | - Modesto Orozco
- Joint BSC-IRB Program on Computational Biology, Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology , Baldiri Reixac 10, Barcelona 08028, Spain
- Departament de Bioquímica i Biomedicina, Facultat de Biologia, Universitat de Barcelona , Avgda Diagonal 647, Barcelona 08028, Spain
| | - Frank Sobott
- Biomolecular & Analytical Mass Spectrometry group, Department of Chemistry, University of Antwerp , 2000 Antwerpen, Belgium
- Astbury Centre for Structural Molecular Biology, University of Leeds , Leeds LS2 9JT, United Kingdom
- School of Molecular and Cellular Biology, University of Leeds , Leeds LS2 9JT, United Kingdom
| | - Rita Grandori
- Department of Biotechnology and Biosciences, University of Milano-Bicocca , Piazza della Scienza 2, 20126 Milan, Italy
| | - Paolo Carloni
- Computational Biomedicine, Institute for Advanced Simulation IAS-5 and Institute of Neuroscience and Medicine INM-9, Forschungszentrum Jülich , 52425 Jülich, Germany
- JARA-HPC, 52425 Jülich, Germany
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Harvey SR, Liu Y, Liu W, Wysocki VH, Laganowsky A. Surface induced dissociation as a tool to study membrane protein complexes. Chem Commun (Camb) 2017; 53:3106-3109. [PMID: 28243658 PMCID: PMC5445643 DOI: 10.1039/c6cc09606a] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Native ion mobility mass spectrometry (MS) and surface induced dissociation (SID) are applied to study the integral membrane protein complexes AmtB and AqpZ. Fragments produced from SID are consistent with the solved structures of these complexes. SID is, therefore, a promising tool for characterization of membrane protein complexes.
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Affiliation(s)
- Sophie R Harvey
- The Department of Chemistry and Biochemistry, The Ohio State University, 460 W 12th Avenue, Columbus, Ohio 43210, USA. and School of Chemistry, Manchester Institute of Biotechnology, University of Manchester, Manchester, M1 7DN, UK
| | - Yang Liu
- Institute of Biosciences and Technology, Texas A&M Health Science Center, Houston, Texas 77030, USA.
| | - Wen Liu
- Institute of Biosciences and Technology, Texas A&M Health Science Center, Houston, Texas 77030, USA.
| | - Vicki H Wysocki
- The Department of Chemistry and Biochemistry, The Ohio State University, 460 W 12th Avenue, Columbus, Ohio 43210, USA.
| | - Arthur Laganowsky
- Institute of Biosciences and Technology, Texas A&M Health Science Center, Houston, Texas 77030, USA. and Department of Chemistry, Texas A&M University, College Station, Texas 77843, USA
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Abstract
In this review, we focus on an important aspect of ion mobility (IM) research, namely the reporting of quantitative ion mobility measurements in the form of the gas-phase collision cross section (CCS), which has provided a common basis for comparison across different instrument platforms and offers a unique form of structural information, namely size and shape preferences of analytes in the absence of bulk solvent. This review surveys the over 24,000 CCS values reported from IM methods spanning the era between 1975 to 2015, which provides both a historical and analytical context for the contributions made thus far, as well as insight into the future directions that quantitative ion mobility measurements will have in the analytical sciences. The analysis was conducted in 2016, so CCS values reported in that year are purposely omitted. In another few years, a review of this scope will be intractable, as the number of CCS values which will be reported in the next three to five years is expected to exceed the total amount currently published in the literature.
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Affiliation(s)
- Jody C May
- Department of Chemistry, Center for Innovative Technology, Vanderbilt Institute for Chemical Biology, Vanderbilt Institute for Integrative Biosystems Research and Education, Vanderbilt University , Nashville, Tennessee 37235, United States
| | - Caleb B Morris
- Department of Chemistry, Center for Innovative Technology, Vanderbilt Institute for Chemical Biology, Vanderbilt Institute for Integrative Biosystems Research and Education, Vanderbilt University , Nashville, Tennessee 37235, United States
| | - John A McLean
- Department of Chemistry, Center for Innovative Technology, Vanderbilt Institute for Chemical Biology, Vanderbilt Institute for Integrative Biosystems Research and Education, Vanderbilt University , Nashville, Tennessee 37235, United States
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36
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Native Mass Spectrometry for the Characterization of Structure and Interactions of Membrane Proteins. Methods Mol Biol 2017; 1635:205-232. [PMID: 28755371 DOI: 10.1007/978-1-4939-7151-0_11] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Over the past years, native mass spectrometry and ion mobility have grown into techniques that are widely applicable to the study of aspects of protein structure. More recently, it has become apparent that this approach provides a very promising avenue for the investigation of integral membrane proteins in lipid or detergent environments.In this chapter, we discuss applications of native mass spectrometry and ion mobility in membrane protein research-what is important to take into consideration when working with membrane proteins, and what the requirements are for sample preparation for native mass spectrometry. Furthermore, we will discuss the types of information provided by the measurements, including the oligomeric state, subunit composition and stoichiometry, interactions with detergents or lipids, conformational transitions, and the binding and structural effect of ligands and drugs.
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Abstract
Membrane proteins play critical physiological roles and make up the majority of drug targets. Due to their generally low expression levels and amphipathic nature, membrane proteins represent challenging molecular entities for biophysical study. Mass spectrometry offers several sensitive approaches to study the biophysics of membrane proteins. By preserving noncovalent interactions in the gas phase and using collisional activation to remove solubilization agents inside the mass spectrometer, native mass spectrometry (MS) is capable of studying isolated assemblies that would be insoluble in aqueous solution, such as membrane protein oligomers and protein-lipid complexes. Conventional methods use detergent to solubilize the protein prior to electrospray ionization. Gas-phase activation inside the mass spectrometer removes the detergent to yield the isolated proteins with bound ligands. This approach has proven highly successful for ionizing membrane proteins. With the appropriate choice of detergents, membrane proteins with bound lipid species can be observed, which allows characterization of protein-lipid interactions. However, detergents have several limitations. They do not necessarily replicate the native lipid bilayer environment, and only a small number of protein-lipid interactions can be resolved. In this Account, we summarize the development of different membrane mimetics as cassettes for MS analysis of membrane proteins. Examples include amphipols, bicelles, and picodiscs with a special emphasis on lipoprotein nanodiscs. Polydispersity and heterogeneity of the membrane mimetic cassette is a critical issue for study by MS. Ever more complex data sets consisting of overlapping protein charge states and multiple lipid-bound entities have required development of new computational, theoretical, and experimental approaches to interpret both mass and ion mobility spectra. We will present the rationale and limitations of these approaches. Starting with the early work on empty nanodiscs, we chart developments that culminate in recent high-resolution studies of membrane protein-lipid complexes ejected from nanodiscs. For the latter, increasing collision energies allowed progressive removal of nanodisc components, beginning with the scaffold proteins and continuing through successive shells of lipids, allowing direct characterization of the stoichiometry of the annular lipid belt that surrounds the membrane protein. We consider future directions for the study of membrane proteins in membrane mimetics, including the development of mixed lipid systems and native bilayer environments. Unambiguous assignment of these heterogeneous systems will rely heavily upon further enhancements in both data analysis protocols and instrumental resolution. We anticipate that these developments will provide new insights into the factors that control dynamic protein-lipid interactions in a variety of tailored and natural lipid environments.
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Affiliation(s)
- Michael T. Marty
- Department of Chemistry, University of Oxford, Physical and Theoretical Chemistry Laboratory, South Parks Road, OX1 3QZ (UK)
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85719 (USA)
| | - Kin Kuan Hoi
- Department of Chemistry, University of Oxford, Physical and Theoretical Chemistry Laboratory, South Parks Road, OX1 3QZ (UK)
| | - Carol V. Robinson
- Department of Chemistry, University of Oxford, Physical and Theoretical Chemistry Laboratory, South Parks Road, OX1 3QZ (UK)
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38
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Dimitrova A, Walko M, Hashemi Shabestari M, Kumar P, Huber M, Kocer A. In situ, Reversible Gating of a Mechanosensitive Ion Channel through Protein-Lipid Interactions. Front Physiol 2016; 7:409. [PMID: 27708587 PMCID: PMC5030285 DOI: 10.3389/fphys.2016.00409] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2016] [Accepted: 08/30/2016] [Indexed: 12/14/2022] Open
Abstract
Understanding the functioning of ion channels, as well as utilizing their properties for biochemical applications requires control over channel activity. Herein we report a reversible control over the functioning of a mechanosensitive ion channel by interfering with its interaction with the lipid bilayer. The mechanosensitive channel of large conductance from Escherichia coli is reconstituted into liposomes and activated to its different sub-open states by titrating lysophosphatidylcholine (LPC) into the lipid bilayer. Activated channels are closed back by the removal of LPC out of the membrane by bovine serum albumin (BSA). Electron paramagnetic resonance spectra showed the LPC-dose-dependent gradual opening of the channel pore in the form of incrementally increasing spin label mobility and decreasing spin-spin interaction. A method to reversibly open and close mechanosensitive channels to distinct sub-open conformations during their journey from the closed to the fully open state enables detailed structural studies to follow the conformational changes during channel functioning. The ability of BSA to revert the action of LPC opens new perspectives for the functional studies of other membrane proteins that are known to be activated by LPC.
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Affiliation(s)
- Anna Dimitrova
- Department of Biochemistry, University of GroningenGroningen, Netherlands
| | - Martin Walko
- Department of Biochemistry, University of GroningenGroningen, Netherlands
| | | | - Pravin Kumar
- Huygens-Kamerlingh Onnes Laboratory, Department of Physics, Leiden UniversityLeiden, Netherlands
| | - Martina Huber
- Huygens-Kamerlingh Onnes Laboratory, Department of Physics, Leiden UniversityLeiden, Netherlands
| | - Armagan Kocer
- Neuroscience Department, University of Groningen, University Medical Center GroningenGroningen, Netherlands
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39
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Allison TM, Landreh M, Benesch JLP, Robinson CV. Low Charge and Reduced Mobility of Membrane Protein Complexes Has Implications for Calibration of Collision Cross Section Measurements. Anal Chem 2016; 88:5879-5884. [PMID: 27153188 DOI: 10.1021/acs.analchem.6b00691] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Ion mobility mass spectrometry of integral membrane proteins provides valuable insights into their architecture and stability. Here we show that, due to their lower charge, the average mobility of native-like membrane protein ions is approximately 30% lower than that of soluble proteins of similar mass. This has implications for drift time measurements, made on traveling wave ion mobility mass spectrometers, which have to be calibrated to extract collision cross sections (Ω). Common calibration strategies employ unfolded or native-like soluble protein standards with masses and mobilities comparable to the protein of interest. We compare Ω values for membrane proteins, derived from standard calibration protocols using soluble proteins, to values measured using an RF-confined drift tube. Our results demonstrate that, while common calibration methods underestimate Ω for native-like or unfolded membrane protein complexes, higher mass soluble calibration standards consistently yield more accurate Ω values. These findings enable us to obtain directly structural information for highly charge-reduced complexes by traveling wave ion mobility mass spectrometry.
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Affiliation(s)
- Timothy M Allison
- Department of Chemistry, Physical & Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford, OX1 3QZ, United Kingdom
| | - Michael Landreh
- Department of Chemistry, Physical & Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford, OX1 3QZ, United Kingdom
| | - Justin L P Benesch
- Department of Chemistry, Physical & Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford, OX1 3QZ, United Kingdom
| | - Carol V Robinson
- Department of Chemistry, Physical & Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford, OX1 3QZ, United Kingdom
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40
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Landreh M, Liko I, Uzdavinys P, Coincon M, Hopper JTS, Drew D, Robinson CV. Controlling release, unfolding and dissociation of membrane protein complexes in the gas phase through collisional cooling. Chem Commun (Camb) 2016; 51:15582-4. [PMID: 26356172 DOI: 10.1039/c5cc07045g] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Mass spectrometry of intact membrane protein complexes requires removal of the detergent micelle by collisional activation. We demonstrate that the necessary energy can be obtained by adjusting the degree of collisional cooling in the ion source. This enables us to extend the energy regime for dissociation of membrane protein complexes.
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Affiliation(s)
- Michael Landreh
- Department of Chemistry, Theoretical and Physical Chemistry Laboratory, University of Oxford, Oxford OX1 3TA, UK.
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41
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PSIONplus: Accurate Sequence-Based Predictor of Ion Channels and Their Types. PLoS One 2016; 11:e0152964. [PMID: 27044036 PMCID: PMC4820270 DOI: 10.1371/journal.pone.0152964] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2015] [Accepted: 03/18/2016] [Indexed: 11/22/2022] Open
Abstract
Ion channels are a class of membrane proteins that attracts a significant amount of basic research, also being potential drug targets. High-throughput identification of these channels is hampered by the low levels of availability of their structures and an observation that use of sequence similarity offers limited predictive quality. Consequently, several machine learning predictors of ion channels from protein sequences that do not rely on high sequence similarity were developed. However, only one of these methods offers a wide scope by predicting ion channels, their types and four major subtypes of the voltage-gated channels. Moreover, this and other existing predictors utilize relatively simple predictive models that limit their accuracy. We propose a novel and accurate predictor of ion channels, their types and the four subtypes of the voltage-gated channels called PSIONplus. Our method combines a support vector machine model and a sequence similarity search with BLAST. The originality of PSIONplus stems from the use of a more sophisticated machine learning model that for the first time in this area utilizes evolutionary profiles and predicted secondary structure, solvent accessibility and intrinsic disorder. We empirically demonstrate that the evolutionary profiles provide the strongest predictive input among new and previously used input types. We also show that all new types of inputs contribute to the prediction. Results on an independent test dataset reveal that PSIONplus obtains relatively good predictive performance and outperforms existing methods. It secures accuracies of 85.4% and 68.3% for the prediction of ion channels and their types, respectively, and the average accuracy of 96.4% for the discrimination of the four ion channel subtypes. Standalone version of PSIONplus is freely available from https://sourceforge.net/projects/psion/
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42
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Reading E, Walton TA, Liko I, Marty MT, Laganowsky A, Rees DC, Robinson CV. The Effect of Detergent, Temperature, and Lipid on the Oligomeric State of MscL Constructs: Insights from Mass Spectrometry. ACTA ACUST UNITED AC 2016; 22:593-603. [PMID: 26000747 DOI: 10.1016/j.chembiol.2015.04.016] [Citation(s) in RCA: 64] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2015] [Revised: 04/23/2015] [Accepted: 04/27/2015] [Indexed: 12/17/2022]
Abstract
The mechanosensitive channel of large conductance (MscL) acts as an emergency release valve for osmotic shock of bacteria preventing cell lysis. The large pore size, essential for function, requires the formation of oligomers with tetramers, pentamers, or hexamers observed depending on the species and experimental approach. We applied non-denaturing (native) mass spectrometry to five different homologs of MscL to determine the oligomeric state under more than 50 different experimental conditions elucidating lipid binding and subunit stoichiometry. We found equilibrium between pentameric and tetrameric species, which can be altered by detergent, disrupted by binding specific lipids, and perturbed by increasing temperature (37°C). We also established the presence of lipopolysaccharide bound to MscL and other membrane proteins expressed in Escherichia coli, revealing a potential source of heterogeneity. More generally, we highlight the use of mass spectrometry in probing membrane proteins under a variety of detergent-lipid environments relevant to structural biology.
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Affiliation(s)
- Eamonn Reading
- Department of Chemistry, Physical & Theoretical Chemistry Laboratory, University of Oxford, Oxford OX1 3TA, UK
| | - Troy A Walton
- Division of Chemistry and Chemical Engineering 114-96, Howard Hughes Medical Institute, California Institute of Technology, Pasadena, CA 91125, USA
| | - Idlir Liko
- Department of Chemistry, Physical & Theoretical Chemistry Laboratory, University of Oxford, Oxford OX1 3TA, UK
| | - Michael T Marty
- Department of Chemistry, Physical & Theoretical Chemistry Laboratory, University of Oxford, Oxford OX1 3TA, UK
| | - Arthur Laganowsky
- Department of Chemistry, Physical & Theoretical Chemistry Laboratory, University of Oxford, Oxford OX1 3TA, UK
| | - Douglas C Rees
- Division of Chemistry and Chemical Engineering 114-96, Howard Hughes Medical Institute, California Institute of Technology, Pasadena, CA 91125, USA
| | - Carol V Robinson
- Department of Chemistry, Physical & Theoretical Chemistry Laboratory, University of Oxford, Oxford OX1 3TA, UK.
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43
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Yefremova Y, Al-Majdoub M, Opuni KF, Koy C, Yan Y, Gross M, Glocker MO. A Dynamic Model of pH-Induced Protein G'e Higher Order Structure Changes derived from Mass Spectrometric Analyses. Anal Chem 2016; 88:890-7. [PMID: 26606592 PMCID: PMC5201196 DOI: 10.1021/acs.analchem.5b03536] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
To obtain insight into pH change-driven molecular dynamics, we studied the higher order structure changes of protein G'e at the molecular and amino acid residue levels in solution by using nanoESI- and IM-mass spectrometry, CD spectroscopy, and protein chemical modification reactions (protein footprinting). We found a dramatic change of the overall tertiary structure of protein G'e when the pH was changed from neutral to acidic, whereas its secondary structure features remained nearly invariable. Limited proteolysis and surface-topology mapping of protein G'e by fast photochemical oxidation of proteins (FPOP) under neutral and acidic conditions reveal areas where higher order conformational changes occur on the amino-acid residue level. Under neutral solution conditions, lower oxidation occurs for residues of the first linker region, whereas greater oxidative modifications occur for amino-acid residues of the IgG-binding domains I and II. We propose a dynamic model of pH-induced structural changes in which protein G'e at neutral pH adopts an overall tight conformation with all four domains packed in a firm assembly, whereas at acidic pH, the three IgG-binding domains form an elongated alignment, and the N-terminal, His-tag-carrying domain unfolds. At the same time the individual IgG-binding domains themselves seem to adopt a more compacted fold. As the secondary structure features are nearly unchanged at either pH, interchange between both conformations is highly reversible, explaining the high reconditioning power of protein G'e-based affinity chromatography columns.
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Affiliation(s)
- Yelena Yefremova
- Proteome Center Rostock, University Medicine Rostock, Rostock, Germany
| | | | | | - Cornelia Koy
- Proteome Center Rostock, University Medicine Rostock, Rostock, Germany
| | - Yuetian Yan
- Department of Chemistry, Washington University in St. Louis, St. Louis, Missouri 63130 USA
| | - Michael Gross
- Department of Chemistry, Washington University in St. Louis, St. Louis, Missouri 63130 USA
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44
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Kocer A. Mechanisms of mechanosensing - mechanosensitive channels, function and re-engineering. Curr Opin Chem Biol 2015; 29:120-7. [PMID: 26610201 DOI: 10.1016/j.cbpa.2015.10.006] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2015] [Revised: 09/30/2015] [Accepted: 10/06/2015] [Indexed: 10/22/2022]
Abstract
Sensing and responding to mechanical stimuli is an ancient behavior and ubiquitous to all forms of life. One of its players 'mechanosensitive ion channels' are involved in processes from osmosensing in bacteria to pain in humans. However, the mechanism of mechanosensing is yet to be elucidated. This review describes recent developments in the understanding of a bacterial mechanosensitive channel. Force from the lipid principle of mechanosensation, new methods to understand protein-lipid interactions, the role of water in the gating, the use of engineered mechanosensitive channels in the understanding of the gating mechanism and application of the accumulated knowledge in the field of drug delivery, drug design and sensor technologies are discussed.
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Affiliation(s)
- Armagan Kocer
- University of Groningen, University Medical Center Groningen, Ant. Deusinglaan 1, 9713 AV Groningen, The Netherlands.
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45
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Affiliation(s)
- Iwona Siuda
- Department of Biological
Sciences and Centre for Molecular Simulation, University of Calgary, 2500 University Drive North West, Calgary, Alberta T2N 1N4, Canada
| | - D. Peter Tieleman
- Department of Biological
Sciences and Centre for Molecular Simulation, University of Calgary, 2500 University Drive North West, Calgary, Alberta T2N 1N4, Canada
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46
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Mechanical coupling of the multiple structural elements of the large-conductance mechanosensitive channel during expansion. Proc Natl Acad Sci U S A 2015; 112:10726-31. [PMID: 26261325 PMCID: PMC4553819 DOI: 10.1073/pnas.1503202112] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
The prokaryotic mechanosensitive channel of large conductance (MscL) is a pressure-relief valve protecting the cell from lysing during acute osmotic downshock. When the membrane is stretched, MscL responds to the increase of membrane tension and opens a nonselective pore to about 30 Å wide, exhibiting a large unitary conductance of ∼ 3 nS. A fundamental step toward understanding the gating mechanism of MscL is to decipher the molecular details of the conformational changes accompanying channel opening. By applying fusion-protein strategy and controlling detergent composition, we have solved the structures of an archaeal MscL homolog from Methanosarcina acetivorans trapped in the closed and expanded intermediate states. The comparative analysis of these two new structures reveals significant conformational rearrangements in the different domains of MscL. The large changes observed in the tilt angles of the two transmembrane helices (TM1 and TM2) fit well with the helix-pivoting model derived from the earlier geometric analyses based on the previous structures. Meanwhile, the periplasmic loop region transforms from a folded structure, containing an ω-shaped loop and a short β-hairpin, to an extended and partly disordered conformation during channel expansion. Moreover, a significant rotating and sliding of the N-terminal helix (N-helix) is coupled to the tilting movements of TM1 and TM2. The dynamic relationships between the N-helix and TM1/TM2 suggest that the N-helix serves as a membrane-anchored stopper that limits the tilts of TM1 and TM2 in the gating process. These results provide direct mechanistic insights into the highly coordinated movement of the different domains of the MscL channel when it expands.
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Yilmaz D, Dimitrova AI, Walko M, Kocer A. Study of light-induced MscL gating by EPR spectroscopy. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2015; 44:557-65. [PMID: 26286445 PMCID: PMC4562997 DOI: 10.1007/s00249-015-1063-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/08/2015] [Revised: 07/14/2015] [Accepted: 07/14/2015] [Indexed: 11/30/2022]
Abstract
A number of techniques developed to investigate protein structure and function depend on chemically modifying and/or labeling of proteins. However, in the case of homooligomeric proteins, the presence of multiple identical subunits obstructs the introduction of residue-specific labels to only one or several subunits, selectively. Here, in order to study the initial conformational changes of a homopentameric mechanosensitive ion channel during its gating, we developed a method for labeling a defined number of subunits of the channel with two different cysteine-specific compounds simultaneously. The first one is a light-sensitive channel activator that determines the degree of openness of the ion channel upon irradiation. The second one is a spin label, containing an unpaired electron, which allows following the resulting structural changes upon channel gating by electron paramagnetic resonance spectroscopy. With this method, we could open MscL into different sub-open states. As the number of light switches per channel increased, the intersubunit spin–spin interactions became less, indicating changes in intersubunit proximities and opening of the channel. The ability of controlled activation of MscL into different open states with a noninvasive trigger and following the resulting conformational changes by spectroscopy will pave the way for detailed spectroscopic studies in the area of mechanosensation.
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Affiliation(s)
- Duygu Yilmaz
- Department of Biochemistry, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands
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Borysik AJ. Structure and dynamics of a protein-surfactant assembly studied by ion-mobility mass spectrometry and molecular dynamics simulations. Anal Chem 2015; 87:8970-6. [PMID: 26266526 DOI: 10.1021/acs.analchem.5b02172] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The structure and dynamics of a protein-surfactant assembly studied by ion-mobility mass spectrometry (IMS) and vacuum molecular dynamics (MD) simulations is reported. Direct evidence is provided for the ability of the surfactant dodecyl-β-D-maltoside (DDM) to prevent charge-induced unfolding of the membrane protein (PagP) in the gas-phase. Restraints obtained by IMS are used to map the surfactant positions onto the protein surface. Surfactants occupying more exposed positions at the apexes of the β-barrel structure are most in-line with the experimental observations. MD simulations provide additional evidence for this assembly organization through surfactant inversion and migration on the protein structure in the absence of solvent. Surfactant migration entails a net shift from apolar membrane spanning regions to more polar regions of the protein structure with the DDM molecule remaining attached to the protein via headgroup interactions. These data provide evidence for the role of protein-DDM headgroup interactions in stabilizing membrane protein structure from gas-phase unfolding.
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Affiliation(s)
- Antoni J Borysik
- Department of Chemistry, King's College London , Britannia House, London SE1 1DB, United Kingdom
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Chi G, Rohde PR, Ridone P, Hankamer B, Martinac B, Landsberg MJ. Functional similarities between heterogeneously and homogenously expressed MscL constructs. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2015; 44:589-98. [PMID: 26233759 DOI: 10.1007/s00249-015-1062-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2015] [Revised: 06/29/2015] [Accepted: 07/14/2015] [Indexed: 11/30/2022]
Abstract
The mechanosensitive channel of large conductance MscL is a well-characterized mechanically gated non-selective ion channel, which often serves as a prototype mechanosensitive channel for mechanotransduction studies. However, there are some discrepancies between MscL constructs used in these studies, most notably unintended heterogeneous expression from some MscL expression constructs. In this study we investigate the possible cause of this expression pattern, and compare the original non-homogenously expressing constructs with our new homogeneously expressing one to confirm that there is little functional difference between them. In addition, a new MscL construct has been developed with an improved molar extinction coefficient at 280 nm, enabling more accurate protein quantification.
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Affiliation(s)
- Gamma Chi
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD, 4072, Australia
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Konijnenberg A, Bannwarth L, Yilmaz D, Koçer A, Venien-Bryan C, Sobott F. Top-down mass spectrometry of intact membrane protein complexes reveals oligomeric state and sequence information in a single experiment. Protein Sci 2015; 24:1292-300. [PMID: 25970171 DOI: 10.1002/pro.2703] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2015] [Revised: 04/24/2015] [Accepted: 04/29/2015] [Indexed: 01/08/2023]
Abstract
Here we study the intact stoichiometry and top-down fragmentation behavior of three integral membrane proteins which were natively reconstituted into detergent micelles: the mechano-sensitive ion channel of large conductance (MscL), the Kirbac potassium channel and the p7 viroporin from the hepatitis C virus. By releasing the proteins under nondenaturing conditions inside the mass spectrometer, we obtained their oligomeric sizes. Increasing the ion activation (collision energy) causes unfolding and subsequent ejection of a highly charged monomer from the membrane protein complexes. Further increase of the ion activation then causes collision-induced dissociation (CID) of the ejected monomers, with fragments observed which were predominantly found to stem from membrane-embedded regions. These experiments show how in a single experiment, we can probe the relation between higher-order structure and protein sequence, by combining the native MS data with fragmentation obtained from top-down MS.
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Affiliation(s)
- Albert Konijnenberg
- Department of Chemistry, Biomolecular & Analytical Mass Spectrometry group, University of Antwerp, Antwerp, Belgium
| | - Ludovic Bannwarth
- Bioinformatique et BioPhysique, Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie (IMPMC), Université Pierre et Marie Curie, Paris, France
| | - Duygu Yilmaz
- Department of Neuroscience, University of Groningen, Groningen, The Netherlands
| | - Armağan Koçer
- Department of Neuroscience, University of Groningen, Groningen, The Netherlands
| | - Catherine Venien-Bryan
- Bioinformatique et BioPhysique, Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie (IMPMC), Université Pierre et Marie Curie, Paris, France
| | - Frank Sobott
- Department of Chemistry, Biomolecular & Analytical Mass Spectrometry group, University of Antwerp, Antwerp, Belgium.,UA-VITO Centre for Proteomics, University of Antwerp, Antwerp, Belgium
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