151
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Hutchings CJ, Colussi P, Clark TG. Ion channels as therapeutic antibody targets. MAbs 2018; 11:265-296. [PMID: 30526315 PMCID: PMC6380435 DOI: 10.1080/19420862.2018.1548232] [Citation(s) in RCA: 74] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2018] [Revised: 11/01/2018] [Accepted: 11/03/2018] [Indexed: 12/12/2022] Open
Abstract
It is now well established that antibodies have numerous potential benefits when developed as therapeutics. Here, we evaluate the technical challenges of raising antibodies to membrane-spanning proteins together with enabling technologies that may facilitate the discovery of antibody therapeutics to ion channels. Additionally, we discuss the potential targeting opportunities in the anti-ion channel antibody landscape, along with a number of case studies where functional antibodies that target ion channels have been reported. Antibodies currently in development and progressing towards the clinic are highlighted.
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Affiliation(s)
| | | | - Theodore G. Clark
- TetraGenetics Inc, Arlington Massachusetts, USA
- Department of Microbiology and Immunology, Cornell University, Ithaca New York, USA
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152
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153
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154
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Membrane protein nanoparticles: the shape of things to come. Biochem Soc Trans 2018; 46:1495-1504. [PMID: 30464048 PMCID: PMC6299238 DOI: 10.1042/bst20180139] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2018] [Revised: 09/23/2018] [Accepted: 10/02/2018] [Indexed: 12/11/2022]
Abstract
The use of styrene–maleic acid (SMA) for the purification of a wide range of membrane proteins (MPs) from both prokaryotic and eukaryotic sources has begun to make an impact in the field of MP biology. This method is growing in popularity as a means to purify and thoroughly investigate the structure and function of MPs and biological membranes. The amphiphilic SMA copolymer can effectively extract MPs directly from a native lipid bilayer to form discs ∼10 nm in diameter. The resulting lipid particles, or styrene–maleic acid lipid particles (SMALPs), contain SMA, protein and membrane lipid. MPs purified in SMALPs are able to retain their native structure and, in many cases, functional activity, and growing evidence suggests that MPs purified using SMA have enhanced thermal stability compared with detergent-purified proteins. The SMALP method is versatile and is compatible with a wide range of cell types across taxonomic domains. It can readily be adapted to replace detergent in many protein purification methods, often with only minor changes made to the existing protocol. Moreover, biophysical analysis and structural determination may now be a possibility for many large, unstable MPs. Here, we review recent advances in the area of SMALP purification and how it is affecting the field of MP biology, critically assess recent progress made with this method, address some of the associated technical challenges which may remain unresolved and discuss opportunities for exploiting SMALPs to expand our understanding of structural and functional properties of MPs.
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155
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Liu Y, Moura ECCM, Dörr JM, Scheidelaar S, Heger M, Egmond MR, Killian JA, Mohammadi T, Breukink E. Bacillus subtilis MraY in detergent-free system of nanodiscs wrapped by styrene-maleic acid copolymers. PLoS One 2018; 13:e0206692. [PMID: 30395652 PMCID: PMC6218056 DOI: 10.1371/journal.pone.0206692] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Accepted: 10/17/2018] [Indexed: 12/25/2022] Open
Abstract
As an integral membrane protein, purification and characterization of phospho-N- acetylmuramyl- pentapeptide translocase MraY have proven difficult. Low yield and concerns of retaining stability and activity after detergent solubilization have hampered the structure-function analysis. The recently developed detergent-free styrene-maleic acid (SMA) co-polymer system offers an alternative approach that may overcome these disadvantages. In this study, we used the detergent free system to purify MraY from Bacillus subtilis. This allowed efficient extraction of MraY that was heterologously produced in Escherichia coli membranes into SMA-wrapped nanodiscs. The purified MraY embedded in these nanodiscs (SMA-MraY) was comparable to the micellar MraY extracted with a conventional detergent (DDM) with regard to the yield and the purity of the recombinant protein but required significantly less time. The predominantly alpha-helical secondary structure of the protein in SMA-wrapped nanodiscs was also more stable against heat denaturation compared to the micellar protein. Thus, this detergent-free system is amenable to extract MraY efficiently and effectively while maintaining the biophysical properties of the protein. However, the apparent activity of the SMA-MraY was reduced compared to that of the detergent-solubilized protein. The present data indicates that this is caused by a lower accessibility of the enzyme in SMA-wrapped nanodiscs towards its polyisoprenoid substrate.
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Affiliation(s)
- Yao Liu
- Department of Membrane Biochemistry and Biophysics, Institute of Biomembranes, Utrecht University, Utrecht, the Netherlands
| | - Elisabete C. C. M. Moura
- Department of Membrane Biochemistry and Biophysics, Institute of Biomembranes, Utrecht University, Utrecht, the Netherlands
| | - Jonas M. Dörr
- Department of Membrane Biochemistry and Biophysics, Institute of Biomembranes, Utrecht University, Utrecht, the Netherlands
| | - Stefan Scheidelaar
- Department of Membrane Biochemistry and Biophysics, Institute of Biomembranes, Utrecht University, Utrecht, the Netherlands
| | - Michal Heger
- Department of Membrane Biochemistry and Biophysics, Institute of Biomembranes, Utrecht University, Utrecht, the Netherlands
- Department of Experimental Surgery, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands
| | - Maarten R. Egmond
- Department of Membrane Biochemistry and Biophysics, Institute of Biomembranes, Utrecht University, Utrecht, the Netherlands
| | - J. Antoinette Killian
- Department of Membrane Biochemistry and Biophysics, Institute of Biomembranes, Utrecht University, Utrecht, the Netherlands
| | - Tamimount Mohammadi
- Department of Membrane Biochemistry and Biophysics, Institute of Biomembranes, Utrecht University, Utrecht, the Netherlands
| | - Eefjan Breukink
- Department of Membrane Biochemistry and Biophysics, Institute of Biomembranes, Utrecht University, Utrecht, the Netherlands
- * E-mail:
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156
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Ravula T, Hardin NZ, Di Mauro GM, Ramamoorthy A. Styrene maleic acid derivates to enhance the applications of bio-inspired polymer based lipid-nanodiscs. Eur Polym J 2018; 108:597-602. [PMID: 31105326 PMCID: PMC6516473 DOI: 10.1016/j.eurpolymj.2018.09.048] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Membrane mimetics are essential to study the structure, dynamics and function of membrane-associated proteins by biophysical and biochemical approaches. Among various membrane mimetics that have been developed and demonstrated for studies on membrane proteins, lipid nanodiscs are the latest developments in the field and are increasingly used for various applications. While lipid-nanodiscs can be formed using an amphipathic membrane scaffold protein (MSP), peptide, or synthetic polymer, the synthetic polymer based nanodiscs exhibit unique advantages because of the ability to functionalize them for various applications. In addition to the use of synthetic polymers to extract membrane proteins directly from the cell membranes, recent advances in the development of polymers used for nanodiscs formation are attracting new attention to the field of nanodiscs technology. Here we review the developments of novel polymer modifications that overcome the current limitations and enhance the applications of polymer based nanodiscs to a wider variety of biophysical techniques used to study membrane proteins. A summary of the functionalization of poly(Styrene-co-Maleic Acid), SMA, polymers developed by our research and their advantages are also covered in this review article.
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Affiliation(s)
- Thirupathi Ravula
- Biophysics Program and Department of Chemistry, The University of Michigan, Ann Arbor, Michigan 48109-1055, USA
| | - Nathaniel. Z Hardin
- Biophysics Program and Department of Chemistry, The University of Michigan, Ann Arbor, Michigan 48109-1055, USA
| | - Giacomo M. Di Mauro
- Biophysics Program and Department of Chemistry, The University of Michigan, Ann Arbor, Michigan 48109-1055, USA
| | - Ayyalusamy Ramamoorthy
- Biophysics Program and Department of Chemistry, The University of Michigan, Ann Arbor, Michigan 48109-1055, USA
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157
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Kwon OS, Song HS, Park TH, Jang J. Conducting Nanomaterial Sensor Using Natural Receptors. Chem Rev 2018; 119:36-93. [DOI: 10.1021/acs.chemrev.8b00159] [Citation(s) in RCA: 113] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Oh Seok Kwon
- Bionanotechnology Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon 34141, Republic of Korea
- Nanobiotechnology and Bioinformatics (Major), University of Science & Technology (UST), Daejon 34141, Republic of Korea
| | - Hyun Seok Song
- Sensor System Research Center, Korea Institute of Science and Technology, Seoul 02792, Republic of Korea
- Division of Bioconvergence Analysis, Korea Basic Science Institute (KBSI), Cheongju 28119, Republic of Korea
- Center for Convergent Research of Emerging Virus Infection, Korea Research Institute of Chemical Technology, Daejeon 34114, Republic of Korea
| | - Tai Hyun Park
- School of Chemical and Biological Engineering, Seoul National University, Seoul 08826, Republic of Korea
| | - Jyongsik Jang
- School of Chemical and Biological Engineering, Seoul National University, Seoul 08826, Republic of Korea
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158
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Smirnova IA, Ädelroth P, Brzezinski P. Extraction and liposome reconstitution of membrane proteins with their native lipids without the use of detergents. Sci Rep 2018; 8:14950. [PMID: 30297885 PMCID: PMC6175888 DOI: 10.1038/s41598-018-33208-1] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2018] [Accepted: 09/25/2018] [Indexed: 11/17/2022] Open
Abstract
Functional studies of membrane-bound channels, transporters or signal transducers require that the protein of interest resides in a membrane that separates two compartments. One approach that is commonly used to prepare these systems is to reconstitute the protein in liposomes. An intermediate step of this method is purification of the protein, which typically involves solubilization of the native membrane using detergent. The use of detergents often results in removal of lipids surrounding the protein, which may alter its structure and function. Here, we have employed a method for isolation of membrane proteins with a disc of their native lipids to develop an approach that allows transfer of the purified membrane protein to liposomes without the use of any detergents.
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Affiliation(s)
- Irina A Smirnova
- Department of Biochemistry and Biophysics, The Arrhenius Laboratories for Natural Sciences, Stockholm University, SE-106 91, Stockholm, Sweden
| | - Pia Ädelroth
- Department of Biochemistry and Biophysics, The Arrhenius Laboratories for Natural Sciences, Stockholm University, SE-106 91, Stockholm, Sweden
| | - Peter Brzezinski
- Department of Biochemistry and Biophysics, The Arrhenius Laboratories for Natural Sciences, Stockholm University, SE-106 91, Stockholm, Sweden.
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159
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Cleary SP, Li H, Bagal D, Loo JA, Campuzano IDG, Prell JS. Extracting Charge and Mass Information from Highly Congested Mass Spectra Using Fourier-Domain Harmonics. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2018; 29:2067-2080. [PMID: 30003534 PMCID: PMC6330157 DOI: 10.1007/s13361-018-2018-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2018] [Revised: 05/30/2018] [Accepted: 06/21/2018] [Indexed: 05/20/2023]
Abstract
Native mass spectra of large, polydisperse biomolecules with repeated subunits, such as lipoprotein Nanodiscs, can often be challenging to analyze by conventional methods. The presence of tens of closely spaced, overlapping peaks in these mass spectra can make charge state, total mass, or subunit mass determinations difficult to measure by traditional methods. Recently, we introduced a Fourier Transform-based algorithm that can be used to deconvolve highly congested mass spectra for polydisperse ion populations with repeated subunits and facilitate identification of the charge states, subunit mass, charge-state-specific, and total mass distributions present in the ion population. Here, we extend this method by investigating the advantages of using overtone peaks in the Fourier spectrum, particularly for mass spectra with low signal-to-noise and poor resolution. This method is illustrated for lipoprotein Nanodisc mass spectra acquired on three common platforms, including the first reported native mass spectrum of empty "large" Nanodiscs assembled with MSP1E3D1 and over 300 noncovalently associated lipids. It is shown that overtone peaks contain nearly identical stoichiometry and charge state information to fundamental peaks but can be significantly better resolved, resulting in more reliable reconstruction of charge-state-specific mass spectra and peak width characterization. We further demonstrate how these parameters can be used to improve results from Bayesian spectral fitting algorithms, such as UniDec. Graphical Abstract ᅟ.
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Affiliation(s)
- Sean P Cleary
- Department of Chemistry and Biochemistry, 1253 University of Oregon, Eugene, OR, 97403-1253, USA
| | - Huilin Li
- Department of Chemistry and Biochemistry, Department of Biological Chemistry, University of California, UCLA/DOE Institute for Genomics and Proteomics, Los Angeles, Los Angeles, CA, 90095, USA
| | - Dhanashri Bagal
- Amgen Discovery Research, Amgen, Inc., 1120 Veterans Blvd, South San Francisco, CA, 94080, USA
| | - Joseph A Loo
- Department of Chemistry and Biochemistry, Department of Biological Chemistry, University of California, UCLA/DOE Institute for Genomics and Proteomics, Los Angeles, Los Angeles, CA, 90095, USA
| | - Iain D G Campuzano
- Molecular Structure and Characterization, Amgen, Inc., Thousand Oaks, CA, 91320, USA
| | - James S Prell
- Department of Chemistry and Biochemistry, 1253 University of Oregon, Eugene, OR, 97403-1253, USA.
- Materials Science Institute, 1252 University of Oregon, Eugene, OR, 97403-1252, USA.
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160
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Yeh V, Lee TY, Chen CW, Kuo PC, Shiue J, Chu LK, Yu TY. Highly Efficient Transfer of 7TM Membrane Protein from Native Membrane to Covalently Circularized Nanodisc. Sci Rep 2018; 8:13501. [PMID: 30201976 PMCID: PMC6131177 DOI: 10.1038/s41598-018-31925-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2018] [Accepted: 08/29/2018] [Indexed: 11/09/2022] Open
Abstract
Incorporating membrane proteins into membrane mimicking systems is an essential process for biophysical studies and structure determination. Monodisperse lipid nanodiscs have been found to be a suitable tool, as they provide a near-native lipid bilayer environment. Recently, a covalently circularized nanodisc (cND) assembled with a membrane scaffold protein (MSP) in circular form, instead of conventional linear form, has emerged. Covalently circularized nanodiscs have been shown to have improved stability, however the optimal strategies for the incorporation of membrane proteins, as well as the physicochemical properties of the membrane protein embedded in the cND, have not been studied. Bacteriorhodopsin (bR) is a seven-transmembrane helix (7TM) membrane protein, and it forms a two dimensional crystal consisting of trimeric bR on the purple membrane of halophilic archea. Here it is reported that the bR trimer in its active form can be directly incorporated into a cND from its native purple membrane. Furthermore, the assembly conditions of the native purple membrane nanodisc (PMND) were optimized to achieve homogeneity and high yield using a high sodium chloride concentration. Additionally, the native PMND was demonstrated to have the ability to assemble over a range of different pHs, suggesting flexibility in the preparation conditions. The native PMND was then found to not only preserve the trimeric structure of bR and most of the native lipids in the PM, but also maintained the photocycle function of bR. This suggests a promising potential for assembling a cND with a 7TM membrane protein, extracted directly from its native membrane environment, while preserving the protein conformation and lipid composition.
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Affiliation(s)
- Vivien Yeh
- Institute of Atomic and Molecular Sciences, Academia Sinica, 1, Sec. 4, Roosevelt Rd., Taipei, 10617, Taiwan.,Department of Chemistry, National Taiwan University, 1, Sec. 4, Roosevelt Rd., Taipei, 10617, Taiwan
| | - Tsung-Yen Lee
- Department of Chemistry, National Tsing Hua University, 101, Sec. 2, Kuang-Fu Rd., Hsinchu, 30013, Taiwan
| | - Chung-Wen Chen
- Institute of Atomic and Molecular Sciences, Academia Sinica, 1, Sec. 4, Roosevelt Rd., Taipei, 10617, Taiwan
| | - Pai-Chia Kuo
- Institute of Physics, Academia Sinica, No.128, Sec. 2, Academia Rd., Taipei, 11529, Taiwan
| | - Jessie Shiue
- Institute of Physics, Academia Sinica, No.128, Sec. 2, Academia Rd., Taipei, 11529, Taiwan
| | - Li-Kang Chu
- Department of Chemistry, National Tsing Hua University, 101, Sec. 2, Kuang-Fu Rd., Hsinchu, 30013, Taiwan.
| | - Tsyr-Yan Yu
- Institute of Atomic and Molecular Sciences, Academia Sinica, 1, Sec. 4, Roosevelt Rd., Taipei, 10617, Taiwan.
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161
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Bibow S, Hiller S. A guide to quantifying membrane protein dynamics in lipids and other native-like environments by solution-state NMR spectroscopy. FEBS J 2018; 286:1610-1623. [PMID: 30133960 DOI: 10.1111/febs.14639] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Revised: 07/04/2018] [Accepted: 08/20/2018] [Indexed: 02/06/2023]
Abstract
Recent biochemical and technical developments permit residue-specific solution NMR measurements of membrane protein (MP) dynamics in lipidic and chaperone-bound environments. This is possible by combinations of improved sample preparations with suitable NMR relaxation experiments to correlate protein function to backbone dynamics on timescales from picoseconds to seconds, even for large MP-lipid assemblies above 100 kDa in molecular mass. Here, we introduce the basic concepts of different NMR relaxation experiments, individually sensitive to specific timescales. We discuss the general limitations of detergent environments and highlight the importance for native-like environments when studying MPs. We then review three practical studies of fast- and slow-timescale MP dynamics in lipid environments, as well as in a natively unfolded, chaperone-bound state. These examples illustrate the new avenues solution NMR spectroscopy is taking to investigate MP dynamics in native-like environments with atomic resolution.
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162
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Methods of reconstitution to investigate membrane protein function. Methods 2018; 147:126-141. [DOI: 10.1016/j.ymeth.2018.02.012] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Accepted: 02/13/2018] [Indexed: 02/06/2023] Open
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163
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Ravula T, Hardin NZ, Bai J, Im SC, Waskell L, Ramamoorthy A. Effect of polymer charge on functional reconstitution of membrane proteins in polymer nanodiscs. Chem Commun (Camb) 2018; 54:9615-9618. [PMID: 30094448 DOI: 10.1039/c8cc04184a] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Although there is a growing interest in using polymer lipid-nanodiscs, the polymer charge poses limitations for studies on membrane proteins. Here, we demonstrate the functional reconstitution of a large soluble-domain containing positively-charged ∼57 kDa cytochrome-P450 and negatively-charged ∼16 kDa cytochrome-b5 in lipid-nanodiscs, and the role of the polymer charge for high-resolution studies on membrane proteins.
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Affiliation(s)
- Thirupathi Ravula
- Biophysics and Department of Chemistry, University of Michigan Ann Arbor, Ann Arbor, MI 48109-1055, USA.
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164
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Schmidt V, Sturgis JN. Modifying Styrene-maleic Acid Co-polymer for Studying Lipid Nanodiscs by Direct Fluorescent Labeling. Bio Protoc 2018; 8:e2969. [PMID: 34395773 DOI: 10.21769/bioprotoc.2969] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2018] [Revised: 07/27/2018] [Accepted: 08/01/2018] [Indexed: 11/02/2022] Open
Abstract
This protocol was developed to functionalize styrene maleic acid (SMA) by direct fluorescent labeling in an easy way, accessible to biochemistry laboratories. This novel method is based on the coupling of carboxylic acids to primary amines using a carbodiimide, a reaction commonly used for protein chemistry. The procedure uses the hydrolyzed styrene-maleic acid copolymer and occurs entirely in aqueous solution with mild conditions compatible with many biomolecules.
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Affiliation(s)
- Victoria Schmidt
- LISM UMR 7255, CNRS and Aix-Marseille University, Marseille cedex 09, France
| | - James N Sturgis
- LISM UMR 7255, CNRS and Aix-Marseille University, Marseille cedex 09, France
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165
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Carlson ML, Young JW, Zhao Z, Fabre L, Jun D, Li J, Li J, Dhupar HS, Wason I, Mills AT, Beatty JT, Klassen JS, Rouiller I, Duong F. The Peptidisc, a simple method for stabilizing membrane proteins in detergent-free solution. eLife 2018; 7:34085. [PMID: 30109849 PMCID: PMC6093710 DOI: 10.7554/elife.34085] [Citation(s) in RCA: 104] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Accepted: 05/05/2018] [Indexed: 12/15/2022] Open
Abstract
Membrane proteins are difficult to work with due to their insolubility in aqueous solution and quite often their poor stability in detergent micelles. Here, we present the peptidisc for their facile capture into water-soluble particles. Unlike the nanodisc, which requires scaffold proteins of different lengths and precise amounts of matching lipids, reconstitution of detergent solubilized proteins in peptidisc only requires a short amphipathic bi-helical peptide (NSPr) and no extra lipids. Multiple copies of the peptide wrap around to shield the membrane-exposed part of the target protein. We demonstrate the effectiveness of this ‘one size fits all’ method using five different membrane protein assemblies (MalFGK2, FhuA, SecYEG, OmpF, BRC) during ‘on-column’, ‘in-gel’, and ‘on-bead’ reconstitution embedded within the membrane protein purification protocol. The peptidisc method is rapid and cost-effective, and it may emerge as a universal tool for high-throughput stabilization of membrane proteins to advance modern biological studies. Surrounding every living cell is a biological membrane that is largely impermeable to water-soluble molecules. This hydrophobic (or “water-hating”) barrier preserves the contents of the cell and also regulates how the cell interacts with its environment. This latter function is critical and relies on a class of proteins that are embedded within the membrane and are also hydrophobic. The hydrophobic nature of membrane proteins is however inconvenient for biochemical studies which usually take place in water-based solutions. Therefore, membrane proteins are under-represented in biological research compared to the water-soluble ones, even though roughly one quarter of a cell’s proteins are membrane proteins. Researchers have developed a few tricks to keep membrane proteins soluble after they have been extracted from the membrane. An old but popular technique makes use of detergents, which are chemicals with opposing hydrophobic and hydrophilic properties (hydrophilic literally means “water-loving”). However, even mild detergents can damage membrane proteins and will sometimes lead to experimental artifacts. More recent tricks to stabilize membrane proteins without detergents have been described but remain laborious, costly or difficult to perform. To overcome these limitations, Carlson et al. developed a simple method to stabilize membrane proteins without detergent. Called the “peptidisc”, the method uses multiple copies of a unique peptide – a short sequence of the building blocks of protein – that had been redesigned to have optimal hydrophobic and hydrophilic properties. The idea was that the peptides would wrap around the hydrophobic parts of the membrane protein, and shield them from the watery solution. Indeed, when Carlson et al. mixed this peptide with five different membrane proteins from bacteria, all were perfectly soluble and functional without detergent. The ideal ratio of peptide needed to form a peptidisc around each membrane protein was reached automatically, without having to test many different conditions. This indicates that the peptidisc acts like a “one size fits all” scaffold. The peptidisc is a new tool that will allow more researchers, including those who are not expert biochemists, to study membrane proteins. This will yield a better understanding of the structure of a cell’s membrane and how it interacts with the environment. Since the approach is both simple and easy to apply, more membrane proteins can now also be included in high-throughput searches for potential new drugs for various medical conditions.
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Affiliation(s)
- Michael Luke Carlson
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, Life Sciences Institute, University of British Columbia, Vancouver, Canada
| | - John William Young
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, Life Sciences Institute, University of British Columbia, Vancouver, Canada
| | - Zhiyu Zhao
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, Life Sciences Institute, University of British Columbia, Vancouver, Canada
| | - Lucien Fabre
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, Life Sciences Institute, University of British Columbia, Vancouver, Canada
| | - Daniel Jun
- Department of Anatomy and Cell Biology, McGill University, Montreal, Canada.,Department of Microbiology and Immunology, University of British Columbia, Vancouver, Canada
| | - Jianing Li
- Glycomics Centre and Department of Chemistry, University of Alberta, Alberta, Canada
| | - Jun Li
- Glycomics Centre and Department of Chemistry, University of Alberta, Alberta, Canada
| | - Harveer Singh Dhupar
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, Life Sciences Institute, University of British Columbia, Vancouver, Canada
| | - Irvin Wason
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, Life Sciences Institute, University of British Columbia, Vancouver, Canada
| | - Allan T Mills
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, Life Sciences Institute, University of British Columbia, Vancouver, Canada
| | - J Thomas Beatty
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, Canada
| | - John S Klassen
- Glycomics Centre and Department of Chemistry, University of Alberta, Alberta, Canada
| | - Isabelle Rouiller
- Department of Anatomy and Cell Biology, McGill University, Montreal, Canada
| | - Franck Duong
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, Life Sciences Institute, University of British Columbia, Vancouver, Canada
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166
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The use of styrene-maleic acid copolymer (SMA) for studies on T cell membrane rafts. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2018; 1861:130-141. [PMID: 30463696 DOI: 10.1016/j.bbamem.2018.08.006] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2018] [Revised: 08/09/2018] [Accepted: 08/13/2018] [Indexed: 02/06/2023]
Abstract
An emerging alternative to the use of detergents in biochemical studies on membrane proteins is apparently the use styrene-maleic acid (SMA) amphipathic copolymers. These cut the membrane into nanodiscs (SMA-lipid particles, SMALPs), which contain membrane proteins possibly surrounded by their native lipid environment. We examined this approach for studies on several types of T cell membrane proteins, previously defined as raft or non-raft associated, to see whether the properties of the raft derived SMALPs differ from non-raft SMALPs. Our results indicate that two types of raft proteins, GPI-anchored proteins and two Src family kinases, are markedly present in membrane fragments much larger (>250 nm) than those containing non-raft proteins (<20 nm). Lipid probes sensitive to membrane fluidity (membrane order) indicate that the lipid environment in the large SMALPs is less fluid (more ordered) than in the small ones which may indicate the presence of a more ordered lipid Lo phase which is characteristic of membrane rafts. Also the lipid composition of the small vs. large SMALPs is markedly different - the large ones are enriched in cholesterol and lipids containing saturated fatty acids. In addition, we confirm that T cell membrane proteins present in SMALPs can be readily immunoisolated. Our results support the use of SMA as a potentially better (less artifact prone) alternative to detergents for studies on membrane proteins and their complexes, including membrane rafts.
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167
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Xue M, Cheng L, Faustino I, Guo W, Marrink SJ. Molecular Mechanism of Lipid Nanodisk Formation by Styrene-Maleic Acid Copolymers. Biophys J 2018; 115:494-502. [PMID: 29980293 PMCID: PMC6084417 DOI: 10.1016/j.bpj.2018.06.018] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2018] [Revised: 05/02/2018] [Accepted: 06/11/2018] [Indexed: 01/06/2023] Open
Abstract
Experimental characterization of membrane proteins often requires solubilization. A recent approach is to use styrene-maleic acid (SMA) copolymers to isolate membrane proteins in nanometer-sized membrane disks, or so-called SMA lipid particles (SMALPs). The approach has the advantage of allowing direct extraction of proteins, keeping their native lipid environment. Despite the growing popularity of using SMALPs, the molecular mechanism behind the process remains poorly understood. Here, we unravel the molecular details of the nanodisk formation by using coarse-grained molecular dynamics simulations. We show how SMA copolymers bind to the lipid bilayer interface, driven by the hydrophobic effect. Due to the concerted action of multiple adsorbed copolymers, large membrane defects appear, including small, water-filled pores. The copolymers can stabilize the rim of these pores, leading to pore growth and membrane disruption. Although complete solubilization is not seen on the timescale of our simulations, self-assembly experiments show that small nanodisks are the thermodynamically preferred end state. Our findings shed light on the mechanism of SMALP formation and on their molecular structure. This can be an important step toward the design of optimized extraction tools for membrane protein research.
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Affiliation(s)
- Minmin Xue
- State Key Laboratory of Mechanics and Control of Mechanical Structures, Key Laboratory for Intelligent Nano Materials and Devices of the Ministry of Education, Institute of Nanoscience, Nanjing University of Aeronautics and Astronautics, Nanjing, People's Republic of China; Groningen Biomolecular Science and Biotechnology Institute, University of Groningen, Groningen, the Netherlands; Zernike Institute for Advanced Materials, University of Groningen, Groningen, the Netherlands
| | - Lisheng Cheng
- College of Mechanical and Electrical Engineering, Beijing University of Chemical Technology, Beijing, People's Republic of China
| | - Ignacio Faustino
- Groningen Biomolecular Science and Biotechnology Institute, University of Groningen, Groningen, the Netherlands; Zernike Institute for Advanced Materials, University of Groningen, Groningen, the Netherlands
| | - Wanlin Guo
- State Key Laboratory of Mechanics and Control of Mechanical Structures, Key Laboratory for Intelligent Nano Materials and Devices of the Ministry of Education, Institute of Nanoscience, Nanjing University of Aeronautics and Astronautics, Nanjing, People's Republic of China
| | - Siewert J Marrink
- Groningen Biomolecular Science and Biotechnology Institute, University of Groningen, Groningen, the Netherlands; Zernike Institute for Advanced Materials, University of Groningen, Groningen, the Netherlands.
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168
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Sgro GG, Costa TRD. Cryo-EM Grid Preparation of Membrane Protein Samples for Single Particle Analysis. Front Mol Biosci 2018; 5:74. [PMID: 30131964 PMCID: PMC6090150 DOI: 10.3389/fmolb.2018.00074] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2018] [Accepted: 07/10/2018] [Indexed: 11/26/2022] Open
Abstract
Recent advances in cryo-electron microscopy (cryo-EM) have made it possible to solve structures of biological macromolecules at near atomic resolution. Development of more stable microscopes, improved direct electron detectors and faster software for image processing has enabled structural solution of not only large macromolecular (megadalton range) complexes but also small (~60 kDa) proteins. As a result of the widespread use of the technique, we have also witnessed new developments of techniques for cryo-EM grid preparation of membrane protein samples. This includes new types of solubilization strategies that better stabilize these protein complexes and the development of new grid supports with proven efficacy in reducing the motion of the molecules during electron beam exposure. Here, we discuss the practicalities and recent challenges of membrane protein sample preparation and vitrification, as well as grid support and foil treatment in the context of the structure determination of protein complexes by single particle cryo-EM.
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Affiliation(s)
- Germán G. Sgro
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, Brazil
| | - Tiago R. D. Costa
- Department of Life Sciences, Imperial College London, MRC Centre for Molecular Microbiology and Infection, London, United Kingdom
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169
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Corradi V, Mendez-Villuendas E, Ingólfsson HI, Gu RX, Siuda I, Melo MN, Moussatova A, DeGagné LJ, Sejdiu BI, Singh G, Wassenaar TA, Delgado Magnero K, Marrink SJ, Tieleman DP. Lipid-Protein Interactions Are Unique Fingerprints for Membrane Proteins. ACS CENTRAL SCIENCE 2018; 4:709-717. [PMID: 29974066 PMCID: PMC6028153 DOI: 10.1021/acscentsci.8b00143] [Citation(s) in RCA: 220] [Impact Index Per Article: 36.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2018] [Indexed: 05/08/2023]
Abstract
Cell membranes contain hundreds of different proteins and lipids in an asymmetric arrangement. Our current understanding of the detailed organization of cell membranes remains rather elusive, because of the challenge to study fluctuating nanoscale assemblies of lipids and proteins with the required spatiotemporal resolution. Here, we use molecular dynamics simulations to characterize the lipid environment of 10 different membrane proteins. To provide a realistic lipid environment, the proteins are embedded in a model plasma membrane, where more than 60 lipid species are represented, asymmetrically distributed between the leaflets. The simulations detail how each protein modulates its local lipid environment in a unique way, through enrichment or depletion of specific lipid components, resulting in thickness and curvature gradients. Our results provide a molecular glimpse of the complexity of lipid-protein interactions, with potentially far-reaching implications for our understanding of the overall organization of real cell membranes.
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Affiliation(s)
- Valentina Corradi
- Centre
for Molecular Simulation and Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada
| | - Eduardo Mendez-Villuendas
- Centre
for Molecular Simulation and Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada
| | - Helgi I. Ingólfsson
- Groningen
Biomolecular Sciences and Biotechnology Institute and Zernike Institute
for Advanced Materials, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | - Ruo-Xu Gu
- Centre
for Molecular Simulation and Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada
| | - Iwona Siuda
- Centre
for Molecular Simulation and Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada
| | - Manuel N. Melo
- Groningen
Biomolecular Sciences and Biotechnology Institute and Zernike Institute
for Advanced Materials, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | - Anastassiia Moussatova
- Centre
for Molecular Simulation and Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada
| | - Lucien J. DeGagné
- Centre
for Molecular Simulation and Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada
| | - Besian I. Sejdiu
- Centre
for Molecular Simulation and Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada
| | - Gurpreet Singh
- Centre
for Molecular Simulation and Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada
| | - Tsjerk A. Wassenaar
- Groningen
Biomolecular Sciences and Biotechnology Institute and Zernike Institute
for Advanced Materials, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | - Karelia Delgado Magnero
- Centre
for Molecular Simulation and Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada
| | - Siewert J. Marrink
- Groningen
Biomolecular Sciences and Biotechnology Institute and Zernike Institute
for Advanced Materials, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | - D. Peter Tieleman
- Centre
for Molecular Simulation and Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada
- E-mail:
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170
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Structure of the alternative complex III in a supercomplex with cytochrome oxidase. Nature 2018; 557:123-126. [PMID: 29695868 PMCID: PMC6004266 DOI: 10.1038/s41586-018-0061-y] [Citation(s) in RCA: 170] [Impact Index Per Article: 28.3] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2017] [Accepted: 03/20/2018] [Indexed: 12/31/2022]
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171
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Mio K, Sato C. Lipid environment of membrane proteins in cryo-EM based structural analysis. Biophys Rev 2018; 10:307-316. [PMID: 29256118 PMCID: PMC5899730 DOI: 10.1007/s12551-017-0371-6] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2017] [Accepted: 11/20/2017] [Indexed: 12/18/2022] Open
Abstract
Cryoelectron microscopy (cryo-EM) in association with a single particle analysis method (SPA) is now a promising tool to determine the structures of proteins and their macromolecular complexes. The development of direct electron detection cameras and image processing technologies has allowed the structures of many important proteins to be solved at near-atomic resolution or, in some cases, at atomic resolution, by overcoming difficulties in crystallization or low yield of protein production. In the case of membrane-integrated proteins, the proteins were traditionally solubilized and stabilized with various kind of detergents. However, the density of detergent micelles diminished the contrast of membrane proteins in cryo-EM studies and made it difficult to obtain high-resolution structures. To improve the resolution of membrane protein structures in cryo-EM studies, major improvements have been made both in sample preparation techniques and in hardware and software developments. The focus of our review is on improvements which have been made in the various techniques for sample preparation for cryo-EM studies, with a specific interest placed on techniques for mimicking the lipid environment of membrane proteins.
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Affiliation(s)
- Kazuhiro Mio
- AIST-UTokyo Advanced Operando-Measurement Technology Open Innovation Laboratory (OPERANDO-OIL), National Institute of Advanced Industrial Science and Technology (AIST), Chiba, 277-8568, Japan.
- Molecular Profiling Research Center for Drug Discovery (molprof), National Institute of Advanced Industrial Science and Technology (AIST), Tokyo, 135-0064, Japan.
| | - Chikara Sato
- Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, 305-8566, Japan.
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172
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Stroud Z, Hall SCL, Dafforn TR. Purification of membrane proteins free from conventional detergents: SMA, new polymers, new opportunities and new insights. Methods 2018; 147:106-117. [PMID: 29608964 DOI: 10.1016/j.ymeth.2018.03.011] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2018] [Revised: 03/19/2018] [Accepted: 03/26/2018] [Indexed: 11/17/2022] Open
Abstract
Membrane proteins remain a somewhat enigmatic group of biomolecules. On the one hand they mediate some of the most important processes in biology with molecular mechanisms that are often elegantly complex. On the other hand they are exceptionally challenging to produce, making studies of membrane protein structure and function among the most difficult projects undertaken by biochemists. The central issue with studies of a membrane protein has been the need to extract them from their native lipid environment before purification and production of a homogenous sample. Historical approaches have utilized detergent solubilisation but these often lead to a sample with low activity and stability. In the past 15 years a new approach that focuses on preserving the local lipid environment surrounding the membrane proteins has been developed. The latest, and perhaps most complete, incarnation of this method has been the use of polymers based on styrene maleic acid (SMA) to stabilise nanoscale discs of lipid that contain membrane proteins. In this review we examine the range of SMA-related polymers that have now been shown to have utility in the production of membrane proteins. We discuss the differences between the polymers and attempt to discover rules and trends that explain their behavior.
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Affiliation(s)
- Zoe Stroud
- School of Biosciences, University of Birmingham, Edgbaston, Birmingham B152TT, UK
| | - Stephen C L Hall
- School of Biosciences, University of Birmingham, Edgbaston, Birmingham B152TT, UK
| | - Tim R Dafforn
- School of Biosciences, University of Birmingham, Edgbaston, Birmingham B152TT, UK.
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173
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Abstract
There are a number of methods of investigating the function of recombinant proteins such as ion channels. However, after channel purification there are few methods to guarantee that the protein still functions. For ion channels, reconstituting back into planar lipid bilayers and demonstrating preserved function is a convenient and trusted method. It is cell free and even inaccessible, intracellular ion channels can be studied. We have used this method to study the function of recombinant channels of known subunit composition and have found it convenient for investigating the mode of action of ion channel modulators.
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Affiliation(s)
- Jacqueline Maher
- School of Pharmacy and Biomolecular Sciences, University Of Brighton, United Kingdom
| | - Marcus Allen
- Centre for Stress and Age-Related Disease, School of Pharmacy and Biomolecular Sciences, University of Brighton, United Kingdom.
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174
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Role of Coulombic Repulsion in Collisional Lipid Transfer Among SMA(2:1)-Bounded Nanodiscs. J Membr Biol 2018; 251:443-451. [DOI: 10.1007/s00232-018-0024-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2017] [Accepted: 02/24/2018] [Indexed: 01/13/2023]
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175
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Ramadugu VSK, Di Mauro GM, Ravula T, Ramamoorthy A. Polymer nanodiscs and macro-nanodiscs of a varying lipid composition. Chem Commun (Camb) 2018; 53:10824-10826. [PMID: 28926036 DOI: 10.1039/c7cc06409h] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Polymer lipid nanodiscs have enabled some exciting structural biology and nanobiotechnology applications. The use of a small molecular weight polymer (SMA-EA) has been demonstrated to dramatically increase the size of nanodiscs (up to ∼60 nm diameter). Here, we report the first demonstration of the formation of macro-nanodiscs for a variety of lipids, and solid-state NMR experiments utilizing their magnetic-alignment properties.
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176
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Penny WM, Palmer CP. Determination of lipid bilayer affinities and solvation characteristics by electrokinetic chromatography using polymer-bound lipid bilayer nanodiscs. Electrophoresis 2018; 39:844-852. [PMID: 29072338 PMCID: PMC5832619 DOI: 10.1002/elps.201700308] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2017] [Revised: 10/12/2017] [Accepted: 10/12/2017] [Indexed: 12/27/2022]
Abstract
Styrene-maleic acid polymer-bound lipid bilayer nanodiscs have been investigated and characterized by electrokinetic chromatography. Linear solvation energy relationship analysis was employed to characterize the changes in solvation environment of nanodiscs of varied belt to lipid ratio, belt polymer chemistry and molecular weight, and lipid composition. Increases in the lipid to belt polymer ratio resulted in smaller, more cohesive nanodiscs with greater electrophoretic mobility. Nanodisc structures with belt polymers of different chemistry and molecular weight were compared and showed only minor changes in solvent characteristics and selectivity consistent with changes in structure of the lipid bilayer. Seven phospholipid and sphingomyelin nanodiscs of different lipid composition were characterized. Changes in lipid head group structure had a significant effect on bilayer-solute interactions. In most cases, changes in alkyl tail structure had no discernible effect on solvation environment aside from those explained by changes in the gel-liquid transition temperature. Comparison to vesicles of similar lipid composition show only minor differences in solvation environment, likely due to differences in lipid composition and bilayer curvature. Together these results provide evidence that the dominant solute-nanodisc interactions are with the lipid bilayer and that head group chemistry has a greater impact on bilayer-solute interactions than alkyl tail or belt polymer structure. Nanodisc electrokinetic chromatography is demonstrated to allow characterization of solute interactions with lipid bilayers of varied composition.
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Affiliation(s)
- William M Penny
- Department of Chemistry and Biochemistry, University of Montana, Missoula, MT, USA
| | - Christopher P Palmer
- Department of Chemistry and Biochemistry, University of Montana, Missoula, MT, USA
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177
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Hardy D, Desuzinges Mandon E, Rothnie AJ, Jawhari A. The yin and yang of solubilization and stabilization for wild-type and full-length membrane protein. Methods 2018; 147:118-125. [PMID: 29477816 DOI: 10.1016/j.ymeth.2018.02.017] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2017] [Revised: 02/12/2018] [Accepted: 02/18/2018] [Indexed: 11/16/2022] Open
Abstract
Membrane proteins (MP) are stable in their native lipid environment. To enable structural and functional investigations, MP need to be extracted from the membrane. This is a critical step that represents the main obstacle for MP biochemistry and structural biology. General guidelines and rules for membrane protein solubilization remain difficult to establish. This review aims to provide the reader with a comprehensive overview of the general concepts of MP solubilization and stabilization as well as recent advances in detergents innovation. Understanding how solubilization and stabilization are intimately linked is key to facilitate MP isolation toward fundamental structural and functional research as well as drug discovery applications. How to manage the tour de force of destabilizing the lipid bilayer and stabilizing MP at the same time is the holy grail of successful isolation and investigation of such a delicate and fascinating class of proteins.
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Affiliation(s)
- David Hardy
- CALIXAR, 60 Avenue Rockefeller, 69008 Lyon, France; Life & Health Sciences, Aston University, Birmingham B4 7ET, UK
| | | | - Alice J Rothnie
- Life & Health Sciences, Aston University, Birmingham B4 7ET, UK
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178
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Parmar M, Rawson S, Scarff CA, Goldman A, Dafforn TR, Muench SP, Postis VLG. Using a SMALP platform to determine a sub-nm single particle cryo-EM membrane protein structure. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2018; 1860:378-383. [PMID: 28993151 PMCID: PMC5780298 DOI: 10.1016/j.bbamem.2017.10.005] [Citation(s) in RCA: 81] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Revised: 10/02/2017] [Accepted: 10/04/2017] [Indexed: 01/10/2023]
Abstract
The field of membrane protein structural biology has been revolutionized over the last few years with a number of high profile structures being solved using cryo-EM including Piezo, Ryanodine receptor, TRPV1 and the Glutamate receptor. Further developments in the EM field hold the promise of even greater progress in terms of greater resolution, which for membrane proteins is still typically within the 4-7Å range. One advantage of a cryo-EM approach is the ability to study membrane proteins in more "native" like environments for example proteoliposomes, amphipols and nanodiscs. Recently, styrene maleic acid co-polymers (SMA) have been used to extract membrane proteins surrounded by native lipids (SMALPs) maintaining a more natural environment. We report here the structure of the Escherichia coli multidrug efflux transporter AcrB in a SMALP scaffold to sub-nm resolution, with the resulting map being consistent with high resolution crystal structures and other EM derived maps. However, both the C-terminal helix (TM12) and TM7 are poorly defined in the map. These helices are at the exterior of the helical bundle and form the greater interaction with the native lipids and SMA polymer and may represent a more dynamic region of the protein. This work shows the promise of using an SMA approach for single particle cryo-EM studies to provide sub-nm structures.
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Affiliation(s)
- Mayuriben Parmar
- Biomedicine Research Group, Faculty of Health and Social Sciences, Leeds Beckett University, LS1 3HE, UK; School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, LS2 9JT, UK
| | - Shaun Rawson
- School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, LS2 9JT, UK; Astbury Centre for Structural Molecular Biology, University of Leeds, LS2 9JT, UK
| | - Charlotte A Scarff
- School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, LS2 9JT, UK; Astbury Centre for Structural Molecular Biology, University of Leeds, LS2 9JT, UK
| | - Adrian Goldman
- School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, LS2 9JT, UK; Astbury Centre for Structural Molecular Biology, University of Leeds, LS2 9JT, UK; Department of Biosciences, Division of Biochemistry, University of Helsinki, Helsinki, Finland
| | - Timothy R Dafforn
- School of Biosciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
| | - Stephen P Muench
- School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, LS2 9JT, UK; Astbury Centre for Structural Molecular Biology, University of Leeds, LS2 9JT, UK.
| | - Vincent L G Postis
- Biomedicine Research Group, Faculty of Health and Social Sciences, Leeds Beckett University, LS1 3HE, UK; School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, LS2 9JT, UK.
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179
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Ravula T, Hardin NZ, Ramadugu SK, Cox SJ, Ramamoorthy A. Formation of pH-Resistant Monodispersed Polymer-Lipid Nanodiscs. Angew Chem Int Ed Engl 2018; 57:1342-1345. [PMID: 29232017 DOI: 10.1002/anie.201712017] [Citation(s) in RCA: 94] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2017] [Indexed: 12/24/2022]
Abstract
Polymer lipid nanodiscs are an invaluable system for structural and functional studies of membrane proteins in their near-native environment. Despite the recent advances in the development and usage of polymer lipid nanodisc systems, lack of control over size and poor tolerance to pH and divalent metal ions are major limitations for further applications. A facile modification of a low-molecular-weight styrene maleic acid copolymer is demonstrated to form monodispersed lipid bilayer nanodiscs that show ultra-stability towards divalent metal ion concentration over a pH range of 2.5 to 10. The macro-nanodiscs (>20 nm diameter) show magnetic alignment properties that can be exploited for high-resolution structural studies of membrane proteins and amyloid proteins using solid-state NMR techniques. The new polymer, SMA-QA, nanodisc is a robust membrane mimetic tool that offers significant advantages over currently reported nanodisc systems.
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Affiliation(s)
- Thirupathi Ravula
- Biophysics Program and Department of Chemistry, University of Michigan, Ann Arbor, MI, 48109-1055, USA
| | - Nathaniel Z Hardin
- Biophysics Program and Department of Chemistry, University of Michigan, Ann Arbor, MI, 48109-1055, USA
| | - Sudheer Kumar Ramadugu
- Biophysics Program and Department of Chemistry, University of Michigan, Ann Arbor, MI, 48109-1055, USA
| | - Sarah J Cox
- Biophysics Program and Department of Chemistry, University of Michigan, Ann Arbor, MI, 48109-1055, USA
| | - Ayyalusamy Ramamoorthy
- Biophysics Program and Department of Chemistry, University of Michigan, Ann Arbor, MI, 48109-1055, USA
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180
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Ravula T, Hardin NZ, Ramadugu SK, Cox SJ, Ramamoorthy A. Formation of pH-Resistant Monodispersed Polymer-Lipid Nanodiscs. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201712017] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Thirupathi Ravula
- Biophysics Program and Department of Chemistry; University of Michigan; Ann Arbor MI 48109-1055 USA
| | - Nathaniel Z. Hardin
- Biophysics Program and Department of Chemistry; University of Michigan; Ann Arbor MI 48109-1055 USA
| | - Sudheer Kumar Ramadugu
- Biophysics Program and Department of Chemistry; University of Michigan; Ann Arbor MI 48109-1055 USA
| | - Sarah J. Cox
- Biophysics Program and Department of Chemistry; University of Michigan; Ann Arbor MI 48109-1055 USA
| | - Ayyalusamy Ramamoorthy
- Biophysics Program and Department of Chemistry; University of Michigan; Ann Arbor MI 48109-1055 USA
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181
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Lippens JL, Nshanian M, Spahr C, Egea PF, Loo JA, Campuzano IDG. Fourier Transform-Ion Cyclotron Resonance Mass Spectrometry as a Platform for Characterizing Multimeric Membrane Protein Complexes. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2018; 29:183-193. [PMID: 28971338 PMCID: PMC5786498 DOI: 10.1007/s13361-017-1799-4] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2017] [Revised: 08/25/2017] [Accepted: 08/26/2017] [Indexed: 05/18/2023]
Abstract
Membrane protein characterization is consistently hampered by challenges with expression, purification, and solubilization. Among several biophysical techniques employed for their characterization, native-mass spectrometry (MS) has emerged as a powerful tool for the analysis of membrane proteins and complexes. Here, two MS platforms, the FT-ICR and Q-ToF, have been explored to analyze the homotetrameric water channel protein, AquaporinZ (AqpZ), under non-denaturing conditions. This 97 kDa membrane protein complex can be readily liberated from the octylglucoside (OG) detergent micelle under a range of instrument conditions on both MS platforms. Increasing the applied collision energy of the FT-ICR collision cell yielded varying degrees of tetramer (97 kDa) liberation from the OG micelles, as well as dissociation into the trimeric (72 kDa) and monomeric (24 kDa) substituents. Tandem-MS on the Q-ToF yielded higher intensity tetramer signal and, depending on the m/z region selected, the observed monomer signal varied in intensity. Precursor ion selection of an m/z range above the expected protein signal distribution, followed by mild collisional activation, is able to efficiently liberate AqpZ with a high S/N ratio. The tetrameric charge state distribution obtained on both instruments demonstrated superpositioning of multiple proteoforms due to varying degrees of N-terminal formylation. Graphical Abstract ᅟ.
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Affiliation(s)
| | - Michael Nshanian
- Department of Chemistry and Biochemistry, University of California-Los Angeles, Los Angeles, CA, 90095, USA
| | - Chris Spahr
- Discovery Attribute Sciences, Amgen, Thousand Oaks, CA, 91320, USA
| | - Pascal F Egea
- Department of Biological Chemistry and Molecular Biology Institute, University of California-Los Angeles, Los Angeles, CA, 90095, USA
| | - Joseph A Loo
- Department of Chemistry and Biochemistry, University of California-Los Angeles, Los Angeles, CA, 90095, USA.
- Department of Biological Chemistry and Molecular Biology Institute, University of California-Los Angeles, Los Angeles, CA, 90095, USA.
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182
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Swainsbury DJK, Proctor MS, Hitchcock A, Cartron ML, Qian P, Martin EC, Jackson PJ, Madsen J, Armes SP, Hunter CN. Probing the local lipid environment of the Rhodobacter sphaeroides cytochrome bc 1 and Synechocystis sp. PCC 6803 cytochrome b 6f complexes with styrene maleic acid. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2017; 1859:215-225. [PMID: 29291373 PMCID: PMC5805856 DOI: 10.1016/j.bbabio.2017.12.005] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/16/2017] [Revised: 12/21/2017] [Accepted: 12/28/2017] [Indexed: 01/21/2023]
Abstract
Intracytoplasmic vesicles (chromatophores) in the photosynthetic bacterium Rhodobacter sphaeroides represent a minimal structural and functional unit for absorbing photons and utilising their energy for the generation of ATP. The cytochrome bc1 complex (cytbc1) is one of the four major components of the chromatophore alongside the reaction centre-light harvesting 1-PufX core complex (RC-LH1-PufX), the light-harvesting 2 complex (LH2), and ATP synthase. Although the membrane organisation of these complexes is known, their local lipid environments have not been investigated. Here we utilise poly(styrene-alt-maleic acid) (SMA) co-polymers as a tool to simultaneously determine the local lipid environments of the RC-LH1-PufX, LH2 and cytbc1 complexes. SMA has previously been reported to effectively solubilise complexes in lipid-rich membrane regions whilst leaving lipid-poor ordered protein arrays intact. Here we show that SMA solubilises cytbc1 complexes with an efficiency of nearly 70%, whereas solubilisation of RC-LH1-PufX and LH2 was only 10% and 22% respectively. This high susceptibility of cytbc1 to SMA solubilisation is consistent with this complex residing in a locally lipid-rich region. SMA solubilised cytbc1 complexes retain their native dimeric structure and co-purify with 56 ± 6 phospholipids from the chromatophore membrane. We extended this approach to the model cyanobacterium Synechocystis sp. PCC 6803, and show that the cytochrome b6f complex (cytb6f) and Photosystem II (PSII) complexes are susceptible to SMA solubilisation, suggesting they also reside in lipid-rich environments. Thus, lipid-rich membrane regions could be a general requirement for cytbc1/cytb6f complexes, providing a favourable local solvent to promote rapid quinol/quinone binding and release at the Q0 and Qi sites. SMA preferentially solubilises cytbc1 from chromatophore membranes. Solubilised cytbc1 SMALPs contain dimeric complexes co-purified with 56 lipids. SMA-resistant fractions contain RC-LH1-PufX and LH2 rich membrane patches. The Rba. sphaeroides cytbc1 complex is likely to reside in a lipid-rich environment. Similar results for Synechocystis suggest cytbc1/b6f may be universally lipid-rich.
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Affiliation(s)
- David J K Swainsbury
- Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, United Kingdom
| | - Matthew S Proctor
- Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, United Kingdom
| | - Andrew Hitchcock
- Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, United Kingdom
| | - Michaël L Cartron
- Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, United Kingdom
| | - Pu Qian
- Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, United Kingdom
| | - Elizabeth C Martin
- Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, United Kingdom
| | - Philip J Jackson
- Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, United Kingdom; ChELSI Institute, Department of Chemical and Biological Engineering, University of Sheffield, Sir Robert Hadfield Building, Mappin Street, Sheffield S1 3JD, United Kingdom
| | - Jeppe Madsen
- Department of Chemistry, University of Sheffield, Brook Hill, Sheffield S3 7HF, United Kingdom
| | - Steven P Armes
- Department of Chemistry, University of Sheffield, Brook Hill, Sheffield S3 7HF, United Kingdom
| | - C Neil Hunter
- Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, United Kingdom.
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183
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Schmidt V, Sturgis JN. Modifying styrene-maleic acid co-polymer for studying lipid nanodiscs. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1860:777-783. [PMID: 29273333 DOI: 10.1016/j.bbamem.2017.12.012] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2017] [Revised: 12/12/2017] [Accepted: 12/14/2017] [Indexed: 01/09/2023]
Abstract
Recently, styrene-maleic acid copolymer lipid nanodiscs have become an increasingly popular tool for the study of membrane proteins. In the work we report here, we have developed a novel method for the efficient preparation of labeled nanodiscs, under chemically mild conditions, by modification of the hydrolyzed styrene-maleic acid copolymer. This protocol is designed to be easily accessible to biochemistry laboratories. We use this procedure to prepare various fluorescent nanodiscs labeled with different fluorophores. By studying the development of Förster resonance energy transfer, we demonstrate the rapid exchange of co-polymer between nanodiscs. This demonstration, in conjunction of previous work, indicates that the lipid nanodiscs prepared using this polymer are very dynamic structures with rapid exchange of the different components.
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Affiliation(s)
- Victoria Schmidt
- LISM UMR 7255, CNRS and Aix-Marseille University, 31 Chemin Joseph Aiguier, Marseille cedex 20 13402, France
| | - James N Sturgis
- LISM UMR 7255, CNRS and Aix-Marseille University, 31 Chemin Joseph Aiguier, Marseille cedex 20 13402, France.
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184
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Yasuhara K, Arakida J, Ravula T, Ramadugu SK, Sahoo B, Kikuchi JI, Ramamoorthy A. Spontaneous Lipid Nanodisc Fomation by Amphiphilic Polymethacrylate Copolymers. J Am Chem Soc 2017; 139:18657-18663. [PMID: 29171274 DOI: 10.1021/jacs.7b10591] [Citation(s) in RCA: 85] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
There is a growing interest in the use of lipid bilayer nanodiscs for various biochemical and biomedical applications. Among the different types of nanodiscs, the unique features of synthetic polymer-based nanodiscs have attracted additional interest. A styrene-maleic acid (SMA) copolymer demonstrated to form lipid nanodiscs has been used for structural biology related studies on membrane proteins. However, the application of SMA polymer based lipid nanodiscs is limited because of the strong absorption of the aromatic group interfering with various experimental measurements. Thus, there is considerable interest in the development of other molecular frameworks for the formation of polymer-based lipid nanodiscs. In this study, we report the first synthesis and characterization of a library of polymethacrylate random copolymers as alternatives to SMA polymer. In addition, we experimentally demonstrate the ability of these polymers to form lipid bilayer nanodiscs through the fragmentation of lipid vesicles by means of light scattering, electron microscopy, differential scanning calorimetry, and solution and solid-state NMR experiments. We further demonstrate a unique application of the newly developed polymer for kinetics and structural characterization of the aggregation of human islet amyloid polypeptide (also known as amylin) within the lipid bilayer of the polymer nanodiscs using thioflavin-T-based fluorescence and circular dichroism experiments. Our results demonstrate that the reported new styrene-free polymers can be used in high-throughput biophysical experiments. Therefore, we expect that the new polymer nanodiscs will be valuable in the structural studies of amyloid proteins and membrane proteins by various biophysical techniques.
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Affiliation(s)
- Kazuma Yasuhara
- Graduate School of Materials Science, Nara Institute of Science and Technology , 8916-5 Takayama-cho, Ikoma, Nara 6300192, Japan
| | - Jin Arakida
- Graduate School of Materials Science, Nara Institute of Science and Technology , 8916-5 Takayama-cho, Ikoma, Nara 6300192, Japan
| | - Thirupathi Ravula
- Biophysics Program and Department of Chemistry, University of Michigan , Ann Arbor, Michigan 48109-1055, United States
| | - Sudheer Kumar Ramadugu
- Biophysics Program and Department of Chemistry, University of Michigan , Ann Arbor, Michigan 48109-1055, United States
| | - Bikash Sahoo
- Biophysics Program and Department of Chemistry, University of Michigan , Ann Arbor, Michigan 48109-1055, United States
| | - Jun-Ichi Kikuchi
- Graduate School of Materials Science, Nara Institute of Science and Technology , 8916-5 Takayama-cho, Ikoma, Nara 6300192, Japan
| | - Ayyalusamy Ramamoorthy
- Biophysics Program and Department of Chemistry, University of Michigan , Ann Arbor, Michigan 48109-1055, United States
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185
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Dominguez Pardo J, Dörr J, Renne M, Ould-Braham T, Koorengevel M, van Steenbergen M, Killian J. Thermotropic properties of phosphatidylcholine nanodiscs bounded by styrene-maleic acid copolymers. Chem Phys Lipids 2017; 208:58-64. [DOI: 10.1016/j.chemphyslip.2017.08.010] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Revised: 08/22/2017] [Accepted: 08/24/2017] [Indexed: 11/15/2022]
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186
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Ravula T, Hardin NZ, Ramadugu SK, Ramamoorthy A. pH Tunable and Divalent Metal Ion Tolerant Polymer Lipid Nanodiscs. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:10655-10662. [PMID: 28920693 DOI: 10.1021/acs.langmuir.7b02887] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The development and applications of detergent-free membrane mimetics have been the focus for the high-resolution structural and functional studies on membrane proteins. The introduction of lipid nanodiscs has attracted new attention toward the structural biology of membrane proteins and also enabled biomedical applications. Lipid nanodiscs provide a native lipid bilayer environment similar to the cell membrane surrounded by a belt made up of proteins or peptides. Recent studies have shown that the hydrolyzed form of styrene maleic anhydride copolymer (SMA) has the ability to form lipid nanodiscs and has several advantages over protein or peptide based nanodiscs. SMA polymer lipid nanodiscs have become very important for structural biology and nanobiotechnological applications. However, applications of the presently available polymer nanodiscs are limited by their instability toward divalent metal ions and acidic conditions. To overcome the limitations of SMA nanodiscs and to broaden the potential applications of polymer nanodiscs, the present study investigates the tunability of SMA polymer nanodiscs by systematically modifying the maleic acid functional group. The two newly developed polymers and subsequent lipid nanodiscs were characterized using solid-state NMR, FT-IR, TEM, and DLS experiments. The pH dependence and metal ion stability of these nanodiscs were studied using static light scattering and FTIR. The reported polymer nanodiscs exhibit unique pH dependent stability based on the modified functional group and show a high tolerance toward divalent metal ions. We also show these tunable nanodiscs can be used to encapsulate and stabilize a polyphenolic natural product curcumin.
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Affiliation(s)
- Thirupathi Ravula
- Biophysics Program and Department of Chemistry, The University of Michigan , Ann Arbor, Michigan 48109-1055, United States
| | - Nathaniel Z Hardin
- Biophysics Program and Department of Chemistry, The University of Michigan , Ann Arbor, Michigan 48109-1055, United States
| | - Sudheer Kumar Ramadugu
- Biophysics Program and Department of Chemistry, The University of Michigan , Ann Arbor, Michigan 48109-1055, United States
| | - Ayyalusamy Ramamoorthy
- Biophysics Program and Department of Chemistry, The University of Michigan , Ann Arbor, Michigan 48109-1055, United States
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187
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Swainsbury DJK, Scheidelaar S, Foster N, van Grondelle R, Killian JA, Jones MR. The effectiveness of styrene-maleic acid (SMA) copolymers for solubilisation of integral membrane proteins from SMA-accessible and SMA-resistant membranes. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2017; 1859:2133-2143. [PMID: 28751090 PMCID: PMC5593810 DOI: 10.1016/j.bbamem.2017.07.011] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/18/2017] [Revised: 07/14/2017] [Accepted: 07/23/2017] [Indexed: 11/27/2022]
Abstract
Solubilisation of biological lipid bilayer membranes for analysis of their protein complement has traditionally been carried out using detergents, but there is increasing interest in the use of amphiphilic copolymers such as styrene maleic acid (SMA) for the solubilisation, purification and characterisation of integral membrane proteins in the form of protein/lipid nanodiscs. Here we survey the effectiveness of various commercially-available formulations of the SMA copolymer in solubilising Rhodobacter sphaeroides reaction centres (RCs) from photosynthetic membranes. We find that formulations of SMA with a 2:1 or 3:1 ratio of styrene to maleic acid are almost as effective as detergent in solubilising RCs, with the best solubilisation by short chain variants (<30kDa weight average molecular weight). The effectiveness of 10kDa 2:1 and 3:1 formulations of SMA to solubilise RCs gradually declined when genetically-encoded coiled-coil bundles were used to artificially tether normally monomeric RCs into dimeric, trimeric and tetrameric multimers. The ability of SMA to solubilise reaction centre-light harvesting 1 (RC-LH1) complexes from densely packed and highly ordered photosynthetic membranes was uniformly low, but could be increased through a variety of treatments to increase the lipid:protein ratio. However, proteins isolated from such membranes comprised clusters of complexes in small membrane patches rather than individual proteins. We conclude that short-chain 2:1 and 3:1 formulations of SMA are the most effective in solubilising integral membrane proteins, but that solubilisation efficiencies are strongly influenced by the size of the target protein and the density of packing of proteins in the membrane.
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Affiliation(s)
- David J K Swainsbury
- School of Biochemistry, University of Bristol, Biomedical Sciences Building, University Walk, Bristol BS8 1TD, United Kingdom
| | - Stefan Scheidelaar
- Membrane Biochemistry & Biophysics, Utrecht University, Bijvoet Center for Biomolecular Research, Utrecht, The Netherlands
| | - Nicholas Foster
- School of Biochemistry, University of Bristol, Biomedical Sciences Building, University Walk, Bristol BS8 1TD, United Kingdom
| | - Rienk van Grondelle
- Division of Physics and Astronomy, VU University Amsterdam, De Boelelaan 1081, Amsterdam 1081 HV, The Netherlands
| | - J Antoinette Killian
- Membrane Biochemistry & Biophysics, Utrecht University, Bijvoet Center for Biomolecular Research, Utrecht, The Netherlands
| | - Michael R Jones
- School of Biochemistry, University of Bristol, Biomedical Sciences Building, University Walk, Bristol BS8 1TD, United Kingdom.
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188
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Grethen A, Oluwole AO, Danielczak B, Vargas C, Keller S. Thermodynamics of nanodisc formation mediated by styrene/maleic acid (2:1) copolymer. Sci Rep 2017; 7:11517. [PMID: 28912575 PMCID: PMC5599547 DOI: 10.1038/s41598-017-11616-z] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2017] [Accepted: 08/29/2017] [Indexed: 12/29/2022] Open
Abstract
Styrene/maleic acid copolymers (SMA) have recently attracted great interest for in vitro studies of membrane proteins, as they self-insert into and fragment biological membranes to form polymer-bounded nanodiscs that provide a native-like lipid-bilayer environment. SMA copolymers are available in different styrene/maleic acid ratios and chain lengths and, thus, possess different charge densities, hydrophobicities, and solubilisation properties. Here, we studied the equilibrium solubilisation properties of the most commonly used copolymer, SMA(2:1), by monitoring the formation of nanodiscs from phospholipid vesicles using 31P nuclear magnetic resonance spectroscopy, dynamic light scattering, and differential scanning calorimetry. Comparison of SMA(2:1) phase diagrams with those of SMA(3:1) and diisobutylene/maleic acid (DIBMA) revealed that, on a mass concentration scale, SMA(2:1) is the most efficient membrane solubiliser, despite its relatively mild effects on the thermotropic phase behaviour of solubilised lipids. In contrast with previous kinetic studies, our equilibrium experiments demonstrate that the solubilisation of phospholipid bilayers by SMA(2:1) is most efficient at moderately alkaline pH values. This pH dependence was also observed for the solubilisation of native Escherichia coli membranes, for which SMA(2:1) again turned out to be the most powerful solubiliser in terms of the total amounts of membrane proteins extracted.
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Affiliation(s)
- Anne Grethen
- Molecular Biophysics, University of Kaiserslautern, 67663, Kaiserslautern, Germany
| | - Abraham Olusegun Oluwole
- Molecular Biophysics, University of Kaiserslautern, 67663, Kaiserslautern, Germany
- Department of Chemistry, University of Ibadan, 200284, Ibadan, Nigeria
| | | | - Carolyn Vargas
- Molecular Biophysics, University of Kaiserslautern, 67663, Kaiserslautern, Germany
| | - Sandro Keller
- Molecular Biophysics, University of Kaiserslautern, 67663, Kaiserslautern, Germany.
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189
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Pollock NL, Lee SC, Patel JH, Gulamhussein AA, Rothnie AJ. Structure and function of membrane proteins encapsulated in a polymer-bound lipid bilayer. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1860:809-817. [PMID: 28865797 DOI: 10.1016/j.bbamem.2017.08.012] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2017] [Revised: 08/18/2017] [Accepted: 08/21/2017] [Indexed: 12/14/2022]
Abstract
New technologies for the purification of stable membrane proteins have emerged in recent years, in particular methods that allow the preparation of membrane proteins with their native lipid environment. Here, we look at the progress achieved with the use of styrene-maleic acid copolymers (SMA) which are able to insert into biological membranes forming nanoparticles containing membrane proteins and lipids. This technology can be applied to membrane proteins from any host source, and, uniquely, allows purification without the protein ever being removed from a lipid bilayer. Not only do these SMA lipid particles (SMALPs) stabilise membrane proteins, allowing structural and functional studies, but they also offer opportunities to understand the local lipid environment of the host membrane. With any new or different method, questions inevitably arise about the integrity of the protein purified: does it retain its activity; its native structure; and ability to perform its function? How do membrane proteins within SMALPS perform in existing assays and lend themselves to analysis by established methods? We outline here recent work on the structure and function of membrane proteins that have been encapsulated like this in a polymer-bound lipid bilayer, and the potential for the future with this approach. This article is part of a Special Issue entitled: Beyond the Structure-Function Horizon of Membrane Proteins edited by Ute Hellmich, Rupak Doshi and Benjamin McIlwain.
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Affiliation(s)
- Naomi L Pollock
- School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
| | - Sarah C Lee
- School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
| | - Jaimin H Patel
- School of Life and Health Sciences, Aston University, Birmingham B4 7ET, UK
| | | | - Alice J Rothnie
- School of Life and Health Sciences, Aston University, Birmingham B4 7ET, UK.
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190
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Dörr JM, van Coevorden-Hameete MH, Hoogenraad CC, Killian JA. Solubilization of human cells by the styrene-maleic acid copolymer: Insights from fluorescence microscopy. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1859:2155-2160. [PMID: 28847501 DOI: 10.1016/j.bbamem.2017.08.010] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2017] [Revised: 08/08/2017] [Accepted: 08/13/2017] [Indexed: 12/20/2022]
Abstract
Extracting membrane proteins from biological membranes by styrene-maleic acid copolymers (SMAs) in the form of nanodiscs has developed into a powerful tool in membrane research. However, the mode of action of membrane (protein) solubilization in a cellular context is still poorly understood and potential specificity for cellular compartments has not been investigated. Here, we use fluorescence microscopy to visualize the process of SMA solubilization of human cells, exemplified by the immortalized human HeLa cell line. Using fluorescent protein fusion constructs that mark distinct subcellular compartments, we found that SMA solubilizes membranes in a concentration-dependent multi-stage process. While all major intracellular compartments were affected without a strong preference, plasma membrane solubilization was found to be generally slower than the solubilization of organelle membranes. Interestingly, some plasma membrane-localized proteins were more resistant against solubilization than others, which might be explained by their presence in specific membrane domains with differing properties. Our results support the general applicability of SMA for the isolation of membrane proteins from different types of (sub)cellular membranes.
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Affiliation(s)
- Jonas M Dörr
- Membrane Biochemistry and Biophysics, Bijvoet Center for Biomolecular Research, Institute of Biomembranes, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
| | | | - Casper C Hoogenraad
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | - J Antoinette Killian
- Membrane Biochemistry and Biophysics, Bijvoet Center for Biomolecular Research, Institute of Biomembranes, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
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191
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Ravula T, Ramadugu SK, Di Mauro G, Ramamoorthy A. Bioinspired, Size-Tunable Self-Assembly of Polymer-Lipid Bilayer Nanodiscs. Angew Chem Int Ed Engl 2017; 56:11466-11470. [PMID: 28714233 DOI: 10.1002/anie.201705569] [Citation(s) in RCA: 109] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Indexed: 11/08/2022]
Abstract
Polymer-based nanodiscs are valuable tools in biomedical research that can offer a detergent-free solubilization of membrane proteins maintaining their native lipid environment. Herein, we introduce a novel ca. 1.6 kDa SMA-based polymer with styrene:maleic acid moieties that can form nanodiscs containing a planar lipid bilayer which are useful to reconstitute membrane proteins for structural and functional studies. The physicochemical properties and the mechanism of formation of polymer-based nanodiscs are characterized by light scattering, NMR, FT-IR, and TEM. A remarkable feature is that nanodiscs of different sizes, from nanometer to sub-micrometer diameter, can be produced by varying the lipid-to-polymer ratio. The small-size nanodiscs (up to ca. 30 nm diameter) can be used for solution NMR spectroscopy studies whereas the magnetic-alignment of macro-nanodiscs (diameter of > ca. 40 nm) can be exploited for solid-state NMR studies on membrane proteins.
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Affiliation(s)
- Thirupathi Ravula
- Biophysics Program and Department of Chemistry, The University of Michigan, Ann Arbor, MI, 48109-1055, USA
| | - Sudheer Kumar Ramadugu
- Biophysics Program and Department of Chemistry, The University of Michigan, Ann Arbor, MI, 48109-1055, USA
| | - Giacomo Di Mauro
- Biophysics Program and Department of Chemistry, The University of Michigan, Ann Arbor, MI, 48109-1055, USA
| | - Ayyalusamy Ramamoorthy
- Biophysics Program and Department of Chemistry, The University of Michigan, Ann Arbor, MI, 48109-1055, USA
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192
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Ravula T, Ramadugu SK, Di Mauro G, Ramamoorthy A. Bioinspired, Size-Tunable Self-Assembly of Polymer-Lipid Bilayer Nanodiscs. Angew Chem Int Ed Engl 2017. [DOI: 10.1002/ange.201705569] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Thirupathi Ravula
- Biophysics Program and Department of Chemistry; The University of Michigan; Ann Arbor MI 48109-1055 USA
| | - Sudheer Kumar Ramadugu
- Biophysics Program and Department of Chemistry; The University of Michigan; Ann Arbor MI 48109-1055 USA
| | - Giacomo Di Mauro
- Biophysics Program and Department of Chemistry; The University of Michigan; Ann Arbor MI 48109-1055 USA
| | - Ayyalusamy Ramamoorthy
- Biophysics Program and Department of Chemistry; The University of Michigan; Ann Arbor MI 48109-1055 USA
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193
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Polymer-encased nanodiscs with improved buffer compatibility. Sci Rep 2017; 7:7432. [PMID: 28785023 PMCID: PMC5547149 DOI: 10.1038/s41598-017-07110-1] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2017] [Accepted: 06/23/2017] [Indexed: 01/07/2023] Open
Abstract
Styrene-maleic acid copolymers allow for solubilization and reconstitution of membrane proteins into nanodiscs. These polymer-encased nanodiscs are promising platforms for studies of membrane proteins in a near-physiologic environment without the use of detergents. However, current styrene-maleic acid copolymers display severe limitations in terms of buffer compatibility and ensued flexibility for various applications. Here, we present a new family of styrene-maleic acid copolymers that do not aggregate at low pH or in the presence of polyvalent cations, and can be used to solubilize membrane proteins and produce nanodiscs of controlled sizes.
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194
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Hu Z, Ho JC, Nallani M. Synthetic (polymer) biology (membrane): functionalization of polymer scaffolds for membrane proteins. Curr Opin Biotechnol 2017; 46:51-56. [DOI: 10.1016/j.copbio.2016.10.012] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2016] [Accepted: 10/24/2016] [Indexed: 12/13/2022]
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195
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Wolf J, Aisenbrey C, Harmouche N, Raya J, Bertani P, Voievoda N, Süss R, Bechinger B. pH-Dependent Membrane Interactions of the Histidine-Rich Cell-Penetrating Peptide LAH4-L1. Biophys J 2017; 113:1290-1300. [PMID: 28734478 DOI: 10.1016/j.bpj.2017.06.053] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2017] [Revised: 06/01/2017] [Accepted: 06/23/2017] [Indexed: 01/17/2023] Open
Abstract
The histidine-rich designer peptide LAH4-L1 exhibits antimicrobial and potent cell-penetrating activities for a wide variety of cargo including nucleic acids, polypeptides, adeno-associated viruses, and nanodots. The non-covalent complexes formed between the peptide and cargo enter the cell via an endosomal pathway where the pH changes from neutral to acidic. Here, we investigated the membrane interactions of the peptide with phospholipid bilayers and its membrane topology using static solid-state NMR spectroscopy. Oriented 15N solid-state NMR indicates that in membranes composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-L-serine (POPS) 3:1 mol/mole and at neutral pH, the peptide adopts transmembrane topologies. Furthermore, 31P and 2H solid-state NMR spectra show that liquid crystalline 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and POPC/POPS 3:1 liposomes retain a bilayer macroscopic phase even at the highest peptide concentrations investigated, with an oblate orientational distribution of the phospholipids at a peptide/lipid ratio of 1:5. At pH 5, as it occurs in the endosome, the alignment of LAH4-L1 at a peptide/lipid ratio of 1:25 is predominantly parallel to POPC/POPS 3:1 bilayers (prolate deformation) when at the same time it induces a considerable decrease of the deuterium order parameter of POPC/2H31-POPS 3:1. In addition, when studied in mechanically supported lipid membranes, a pronounced disordering of the phospholipid alignment is observed. In the presence of even higher peptide concentrations, lipid spectra are observed that suggest the formation of magnetically oriented or isotropic bicelles. This membrane-disruptive effect is enhanced for gel phase DMPC membranes. By protonation of the four histidines in acidic environments, the overall charge and hydrophobic moment of LAH4-L1 considerably change, and much of the peptide is released from the cargo. Thus, the amphipathic peptide sequences become available to disrupt the endosomal membrane and to assure highly efficient release from this organelle.
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Affiliation(s)
- Justine Wolf
- Institut de Chimie, UMR7177, Université de Strasbourg, CNRS, Strasbourg, France
| | | | - Nicole Harmouche
- Institut de Chimie, UMR7177, Université de Strasbourg, CNRS, Strasbourg, France
| | - Jesus Raya
- Institut de Chimie, UMR7177, Université de Strasbourg, CNRS, Strasbourg, France
| | - Philippe Bertani
- Institut de Chimie, UMR7177, Université de Strasbourg, CNRS, Strasbourg, France
| | - Natalia Voievoda
- Institut de Chimie, UMR7177, Université de Strasbourg, CNRS, Strasbourg, France
| | - Regine Süss
- Albert-Ludwigs-Universität Freiburg, Pharmazeutische Technologie und Biopharmazie, Freiburg, Germany
| | - Burkhard Bechinger
- Institut de Chimie, UMR7177, Université de Strasbourg, CNRS, Strasbourg, France.
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196
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Abstract
The use of styrene maleic acid lipid particles (SMALPs) for the purification of membrane proteins (MPs) is a rapidly developing technology. The amphiphilic copolymer of styrene and maleic acid (SMA) disrupts biological membranes and can extract membrane proteins in nanodiscs of approximately 10 nm diameter. These discs contain SMA, protein and membrane lipids. There is evidence that MPs in SMALPs retain their native structures and functions, in some cases with enhanced thermal stability. In addition, the method is compatible with biological buffers and a wide variety of biophysical and structural analysis techniques. The use of SMALPs to solubilize and stabilize MPs offers a new approach in our attempts to understand, and influence, the structure and function of MPs and biological membranes. In this review, we critically assess progress with this method, address some of the associated technical challenges, and discuss opportunities for exploiting SMA and SMALPs to expand our understanding of MP biology.
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197
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Abstract
To study integral membrane proteins, one has to extract them from the membrane—the step that is typically achieved by the application of detergents. In this mini-review, we summarize the top 10 detergents used for the structural analysis of membrane proteins based on the published results. The aim of this study is to provide the reader with an overview of the main properties of available detergents (critical micelle concentration (CMC) value, micelle size, etc.) and provide an idea of what detergents to may merit further study. Furthermore, we briefly discuss alternative solubilization and stabilization agents, such as polymers.
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198
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Morris RG. Signatures of Mechanosensitive Gating. Biophys J 2017; 112:3-9. [PMID: 28076813 DOI: 10.1016/j.bpj.2016.12.009] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2016] [Revised: 12/05/2016] [Accepted: 12/07/2016] [Indexed: 01/10/2023] Open
Abstract
The question of how mechanically gated membrane channels open and close is notoriously difficult to address, especially if the protein structure is not available. This perspective highlights the relevance of micropipette-aspirated single-particle tracking-used to obtain a channel's diffusion coefficient, D, as a function of applied membrane tension, σ-as an indirect assay for determining functional behavior in mechanosensitive channels. While ensuring that the protein remains integral to the membrane, such methods can be used to identify not only the gating mechanism of a protein, but also associated physical moduli, such as torsional and dilational rigidity, which correspond to the protein's effective shape change. As an example, three distinct D-versus-σ "signatures" are calculated, corresponding to gating by dilation, gating by tilt, and gating by a combination of both dilation and tilt. Both advantages and disadvantages of the approach are discussed.
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Affiliation(s)
- Richard G Morris
- National Centre for Biological Sciences, Tata Institute for Fundamental Research, GKVK, Bangalore, India.
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199
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Overcoming bottlenecks in the membrane protein structural biology pipeline. Biochem Soc Trans 2017; 44:838-44. [PMID: 27284049 DOI: 10.1042/bst20160049] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2016] [Indexed: 02/07/2023]
Abstract
Membrane proteins account for a third of the eukaryotic proteome, but are greatly under-represented in the Protein Data Bank. Unfortunately, recent technological advances in X-ray crystallography and EM cannot account for the poor solubility and stability of membrane protein samples. A limitation of conventional detergent-based methods is that detergent molecules destabilize membrane proteins, leading to their aggregation. The use of orthologues, mutants and fusion tags has helped improve protein stability, but at the expense of not working with the sequence of interest. Novel detergents such as glucose neopentyl glycol (GNG), maltose neopentyl glycol (MNG) and calixarene-based detergents can improve protein stability without compromising their solubilizing properties. Styrene maleic acid lipid particles (SMALPs) focus on retaining the native lipid bilayer of a membrane protein during purification and biophysical analysis. Overcoming bottlenecks in the membrane protein structural biology pipeline, primarily by maintaining protein stability, will facilitate the elucidation of many more membrane protein structures in the near future.
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200
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Applications of NMR to membrane proteins. Arch Biochem Biophys 2017; 628:92-101. [PMID: 28529197 DOI: 10.1016/j.abb.2017.05.011] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Revised: 05/15/2017] [Accepted: 05/17/2017] [Indexed: 01/14/2023]
Abstract
Membrane proteins present a challenge for structural biology. In this article, we review some of the recent developments that advance the application of NMR to membrane proteins, with emphasis on structural studies in detergent-free, lipid bilayer samples that resemble the native environment. NMR spectroscopy is not only ideally suited for structure determination of membrane proteins in hydrated lipid bilayer membranes, but also highly complementary to the other principal techniques based on X-ray and electron diffraction. Recent advances in NMR instrumentation, spectroscopic methods, computational methods, and sample preparations are driving exciting new efforts in membrane protein structural biology.
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