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Abstract
TonB-dependent transporters (TBDTs) are present in all gram-negative bacteria and mediate energy-dependent uptake of molecules that are too scarce or large to be taken up efficiently by outer membrane (OM) diffusion channels. This process requires energy that is derived from the proton motive force and delivered to TBDTs by the TonB-ExbBD motor complex in the inner membrane. Together with the need to preserve the OM permeability barrier, this has led to an extremely complex and fascinating transport mechanism for which the fundamentals, despite decades of research, are still unclear. In this review, we describe our current understanding of the transport mechanism of TBDTs, their potential role in the delivery of novel antibiotics, and the important contributions made by TBDT-associated (lipo)proteins.
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Affiliation(s)
- Augustinas Silale
- Biosciences Institute, The Medical School, Newcastle University, Newcastle upon Tyne, United Kingdom; ,
| | - Bert van den Berg
- Biosciences Institute, The Medical School, Newcastle University, Newcastle upon Tyne, United Kingdom; ,
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2
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Mayse LA, Movileanu L. Gating of β-Barrel Protein Pores, Porins, and Channels: An Old Problem with New Facets. Int J Mol Sci 2023; 24:12095. [PMID: 37569469 PMCID: PMC10418385 DOI: 10.3390/ijms241512095] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2023] [Revised: 07/23/2023] [Accepted: 07/25/2023] [Indexed: 08/13/2023] Open
Abstract
β barrels are ubiquitous proteins in the outer membranes of mitochondria, chloroplasts, and Gram-negative bacteria. These transmembrane proteins (TMPs) execute a wide variety of tasks. For example, they can serve as transporters, receptors, membrane-bound enzymes, as well as adhesion, structural, and signaling elements. In addition, multimeric β barrels are common structural scaffolds among many pore-forming toxins. Significant progress has been made in understanding the functional, structural, biochemical, and biophysical features of these robust and versatile proteins. One frequently encountered fundamental trait of all β barrels is their voltage-dependent gating. This process consists of reversible or permanent conformational transitions between a large-conductance, highly permeable open state and a low-conductance, solute-restrictive closed state. Several intrinsic molecular mechanisms and environmental factors modulate this universal property of β barrels. This review article outlines the typical signatures of voltage-dependent gating. Moreover, we discuss recent developments leading to a better qualitative understanding of the closure dynamics of these TMPs.
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Affiliation(s)
- Lauren A. Mayse
- Department of Physics, Syracuse University, 201 Physics Building, Syracuse, NY 13244, USA;
- Department of Biomedical and Chemical Engineering, Syracuse University, 223 Link Hall, Syracuse, NY 13244, USA
| | - Liviu Movileanu
- Department of Physics, Syracuse University, 201 Physics Building, Syracuse, NY 13244, USA;
- Department of Biomedical and Chemical Engineering, Syracuse University, 223 Link Hall, Syracuse, NY 13244, USA
- The BioInspired Institute, Syracuse University, Syracuse, NY 13244, USA
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3
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Young JW, Zhao Z, Wason IS, Duong van Hoa F. A Dual Detergent Strategy to Capture a Bacterial Outer Membrane Proteome in Peptidiscs for Characterization by Mass Spectrometry and Binding Assays. J Proteome Res 2022; 22:1537-1545. [PMID: 36516475 DOI: 10.1021/acs.jproteome.2c00560] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The outer membrane of Gram-negative bacteria plays a critical role in protecting the cell against external stressors, including antibiotics, and therefore is a prime target for antimicrobial discovery. To facilitate the discovery efforts, a precise knowledge of the outer membrane proteome, and possible variations during pathogenesis, is important. Characterization of the bacterial outer membrane remain challenging, however, and low throughput, due to the high hydrophobicity and relatively low abundance of this cell compartment. Here we adapt our peptidisc-based method to selectively isolate the outer membrane proteome before analysis by mass spectrometry. Using a dual detergent membrane solubilization approach, followed by protein purification in peptidiscs, we capture over 70 outer membrane proteins, including 26 integral β-barrels and 26 lipoproteins. Many of these proteins are present at high peptide intensities, indicative of a high abundance in the library sample. We further show that the isolated outer membrane proteome can be employed in downstream ligand-binding assays. This peptidisc library made of outer membrane proteins may therefore be useful to systematically survey other bacterial outer membrane proteomes, but also as a nanoparticle format able to support the discovery of next-generation antimicrobials. Data are available via ProteomeXchange identifier PXD036749.
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Affiliation(s)
- John William Young
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Zhiyu Zhao
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Irvinder Singh Wason
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Franck Duong van Hoa
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
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4
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Biophysical characterisation of SMALPs. Biochem Soc Trans 2021; 49:2037-2050. [PMID: 34643233 DOI: 10.1042/bst20201088] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2021] [Revised: 09/22/2021] [Accepted: 09/23/2021] [Indexed: 11/17/2022]
Abstract
Membrane proteins such as receptors, ion channels and transport proteins are important drug targets. The structure-based study of membrane proteins is challenging, especially when the target protein contains both soluble and insoluble domains. Most membrane proteins are insoluble in aqueous solvent and embedded in the plasma membrane lipid bilayer, which significantly complicates biophysical studies. Poly(styrene-co-maleic acid) (SMA) and other polymer derivatives are increasingly common solubilisation agents, used to isolate membrane proteins stabilised in their native lipid environment in the total absence of detergent. Since the initial report of SMA-mediated solubilisation, and the formation of SMA lipid particles (SMALPs), this technique can directly isolate therapeutic targets from biological membranes, including G-protein coupled receptors (GPCRs). SMA now allows biophysical and structural analyses of membrane proteins in solution that was not previously possible. Here, we critically review several existing biophysical techniques compatible with SMALPs, with a focus on hydrodynamic analysis, microcalorimetric analysis and optical spectroscopic techniques.
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5
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Josts I, Veith K, Tidow H. Ternary structure of the outer membrane transporter FoxA with resolved signalling domain provides insights into TonB-mediated siderophore uptake. eLife 2019; 8:48528. [PMID: 31385808 PMCID: PMC6699858 DOI: 10.7554/elife.48528] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2019] [Accepted: 08/05/2019] [Indexed: 01/27/2023] Open
Abstract
Many microbes and fungi acquire the essential ion Fe3+ through the synthesis and secretion of high-affinity chelators termed siderophores. In Gram-negative bacteria, these ferric-siderophore complexes are actively taken up using highly specific TonB-dependent transporters (TBDTs) located in the outer bacterial membrane (OM). However, the detailed mechanism of how the inner-membrane protein TonB connects to the transporters in the OM as well as the interplay between siderophore- and TonB-binding to the transporter is still poorly understood. Here, we present three crystal structures of the TBDT FoxA from Pseudomonas aeruginosa (containing a signalling domain) in complex with the siderophore ferrioxamine B and TonB and combine them with a detailed analysis of binding constants. The structures show that both siderophore and TonB-binding is required to form a translocation-competent state of the FoxA transporter in a two-step TonB-binding mechanism. The complex structure also indicates how TonB-binding influences the orientation of the signalling domain.
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Affiliation(s)
- Inokentijs Josts
- The Hamburg Centre for Ultrafast Imaging, University of Hamburg, Hamburg, Germany.,Department of Chemistry, Institute for Biochemistry and Molecular Biology, University of Hamburg, Hamburg, Germany
| | - Katharina Veith
- The Hamburg Centre for Ultrafast Imaging, University of Hamburg, Hamburg, Germany.,Department of Chemistry, Institute for Biochemistry and Molecular Biology, University of Hamburg, Hamburg, Germany
| | - Henning Tidow
- The Hamburg Centre for Ultrafast Imaging, University of Hamburg, Hamburg, Germany.,Department of Chemistry, Institute for Biochemistry and Molecular Biology, University of Hamburg, Hamburg, Germany
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6
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Keener JE, Zambrano DE, Zhang G, Zak CK, Reid DJ, Deodhar BS, Pemberton JE, Prell JS, Marty MT. Chemical Additives Enable Native Mass Spectrometry Measurement of Membrane Protein Oligomeric State within Intact Nanodiscs. J Am Chem Soc 2019; 141:1054-1061. [PMID: 30586296 DOI: 10.1021/jacs.8b11529] [Citation(s) in RCA: 61] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Membrane proteins play critical biochemical roles but remain challenging to study. Recently, native or nondenaturing mass spectrometry (MS) has made great strides in characterizing membrane protein interactions. However, conventional native MS relies on detergent micelles, which may disrupt natural interactions. Lipoprotein nanodiscs provide a platform to present membrane proteins for native MS within a lipid bilayer environment, but previous native MS of membrane proteins in nanodiscs has been limited by the intermediate stability of nanodiscs. It is difficult to eject membrane proteins from nanodiscs for native MS but also difficult to retain intact nanodisc complexes with membrane proteins inside. Here, we employed chemical reagents that modulate the charge acquired during electrospray ionization (ESI). By modulating ESI conditions, we could either eject the membrane protein complex with few bound lipids or capture the intact membrane protein nanodisc complex-allowing measurement of the membrane protein oligomeric state within an intact lipid bilayer environment. The dramatic differences in the stability of nanodiscs under different ESI conditions opens new applications for native MS of nanodiscs.
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Affiliation(s)
- James E Keener
- Department of Chemistry and Biochemistry , University of Arizona , Tucson , Arizona 85721 , United States
| | - Dane Evan Zambrano
- Department of Chemistry and Biochemistry , University of Arizona , Tucson , Arizona 85721 , United States
| | - Guozhi Zhang
- Department of Chemistry and Biochemistry , University of Arizona , Tucson , Arizona 85721 , United States
| | - Ciara K Zak
- Department of Chemistry and Biochemistry , University of Arizona , Tucson , Arizona 85721 , United States
| | - Deseree J Reid
- Department of Chemistry and Biochemistry , University of Arizona , Tucson , Arizona 85721 , United States
| | - Bhushan S Deodhar
- Department of Chemistry and Biochemistry , University of Arizona , Tucson , Arizona 85721 , United States
| | - Jeanne E Pemberton
- Department of Chemistry and Biochemistry , University of Arizona , Tucson , Arizona 85721 , United States
| | - James S Prell
- Department of Chemistry and Biochemistry , University of Oregon , Eugene , Oregon 97403 , United States
| | - Michael T Marty
- Department of Chemistry and Biochemistry , University of Arizona , Tucson , Arizona 85721 , United States
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7
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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: 100] [Impact Index Per Article: 16.7] [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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8
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Substrate-bound outward-open structure of a Na +-coupled sialic acid symporter reveals a new Na + site. Nat Commun 2018; 9:1753. [PMID: 29717135 PMCID: PMC5931594 DOI: 10.1038/s41467-018-04045-7] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2017] [Accepted: 03/28/2018] [Indexed: 01/03/2023] Open
Abstract
Many pathogenic bacteria utilise sialic acids as an energy source or use them as an external coating to evade immune detection. As such, bacteria that colonise sialylated environments deploy specific transporters to mediate import of scavenged sialic acids. Here, we report a substrate-bound 1.95 Å resolution structure and subsequent characterisation of SiaT, a sialic acid transporter from Proteus mirabilis. SiaT is a secondary active transporter of the sodium solute symporter (SSS) family, which use Na+ gradients to drive the uptake of extracellular substrates. SiaT adopts the LeuT-fold and is in an outward-open conformation in complex with the sialic acid N-acetylneuraminic acid and two Na+ ions. One Na+ binds to the conserved Na2 site, while the second Na+ binds to a new position, termed Na3, which is conserved in many SSS family members. Functional and molecular dynamics studies validate the substrate-binding site and demonstrate that both Na+ sites regulate N-acetylneuraminic acid transport.
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9
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Moon S, Kong B, Jung YH, Kim Y, Yu S, Park JB, Shin J, Kweon DH. Endotoxin-free purification of recombinant membrane scaffold protein expressed in Escherichia coli. Process Biochem 2018. [DOI: 10.1016/j.procbio.2017.12.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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10
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Thakur AK, Larimi MG, Gooden K, Movileanu L. Aberrantly Large Single-Channel Conductance of Polyhistidine Arm-Containing Protein Nanopores. Biochemistry 2017; 56:4895-4905. [PMID: 28812882 DOI: 10.1021/acs.biochem.7b00577] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
There have been only a few studies reporting on the impact of polyhistidine affinity tags on the structure, function, and dynamics of proteins. Because of the relatively short size of the tags, they are often thought to have little or no effect on the conformation or activity of a protein. Here, using membrane protein design and single-molecule electrophysiology, we determined that the presence of a hexahistidine arm at the N-terminus of a truncated FhuA-based protein nanopore, leaving the C-terminus untagged, produces an unusual increase in the unitary conductance to ∼8 nS in 1 M KCl. To the best of our knowledge, this is the largest single-channel conductance ever recorded with a monomeric β-barrel outer membrane protein. The hexahistidine arm was captured by an anti-polyhistidine tag monoclonal antibody added to the side of the channel-forming protein addition, but not to the opposite side, documenting that this truncated FhuA-based protein nanopore inserts into a planar lipid bilayer with a preferred orientation. This finding is in agreement with the protein insertion in vivo, in which the large loops face the extracellular side of the membrane. The aberrantly large single-channel conductance, likely induced by a greater cross-sectional area of the pore lumen, along with the vectorial insertion into a lipid membrane, will have profound implications for further developments of engineered protein nanopores.
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Affiliation(s)
- Avinash Kumar Thakur
- Department of Physics, Syracuse University , 201 Physics Building, Syracuse, New York 13244-1130, United States.,Structural Biology, Biochemistry, and Biophysics Program, Syracuse University , 111 College Place, Syracuse, New York 13244-4100, United States
| | - Motahareh Ghahari Larimi
- Department of Physics, Syracuse University , 201 Physics Building, Syracuse, New York 13244-1130, United States
| | - Kristin Gooden
- Department of Physics and Astronomy, University of Missouri , 223 Physics Building, Columbia, Missouri 65211-7010, United States
| | - Liviu Movileanu
- Department of Physics, Syracuse University , 201 Physics Building, Syracuse, New York 13244-1130, United States.,Structural Biology, Biochemistry, and Biophysics Program, Syracuse University , 111 College Place, Syracuse, New York 13244-4100, United States.,Department of Biomedical and Chemical Engineering, Syracuse University , 329 Link Hall, Syracuse, New York 13244, United States
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11
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Rouck J, Krapf J, Roy J, Huff H, Das A. Recent advances in nanodisc technology for membrane protein studies (2012-2017). FEBS Lett 2017; 591:2057-2088. [PMID: 28581067 PMCID: PMC5751705 DOI: 10.1002/1873-3468.12706] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2017] [Revised: 05/26/2017] [Accepted: 05/31/2017] [Indexed: 01/01/2023]
Abstract
Historically, the main barrier to membrane protein investigations has been the tendency of membrane proteins to aggregate (due to their hydrophobic nature), in aqueous solution as well as on surfaces. The introduction of biomembrane mimetics has since stimulated momentum in the field. One such mimetic, the nanodisc (ND) system, has proved to be an exceptional system for solubilizing membrane proteins. Herein, we critically evaluate the advantages and imperfections of employing nanodiscs in biophysical and biochemical studies. Specifically, we examine the techniques that have been modified to study membrane proteins in nanodiscs. Techniques discussed here include fluorescence microscopy, solution-state/solid-state nuclear magnetic resonance, electron microscopy, small-angle X-ray scattering, and several mass spectroscopy methods. Newer techniques such as SPR, charge-sensitive optical detection, and scintillation proximity assays are also reviewed. Lastly, we cover how nanodiscs are advancing nanotechnology through nanoplasmonic biosensing, lipoprotein-nanoplatelets, and sortase-mediated labeling of nanodiscs.
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Affiliation(s)
- John Rouck
- Department of Biochemistry, University of Illinois Urbana–Champaign, Urbana IL 61802, USA
| | - John Krapf
- Department of Biochemistry, University of Illinois Urbana–Champaign, Urbana IL 61802, USA
| | - Jahnabi Roy
- Department of Chemistry, University of Illinois Urbana–Champaign, Urbana IL 61802, USA
| | - Hannah Huff
- Department of Chemistry, University of Illinois Urbana–Champaign, Urbana IL 61802, USA
| | - Aditi Das
- Department of Comparative Biosciences, University of Illinois Urbana–Champaign, Urbana IL 61802, USA
- Department of Biochemistry, University of Illinois Urbana–Champaign, Urbana IL 61802, USA
- Beckman Institute for Advanced Science, Division of Nutritional Sciences, Neuroscience Program and Department of Bioengineering, University of Illinois Urbana–Champaign, Urbana IL 61802, USA
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12
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TonB-dependent ligand trapping in the BtuB transporter. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1858:3105-3112. [DOI: 10.1016/j.bbamem.2016.09.019] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Revised: 09/21/2016] [Accepted: 09/22/2016] [Indexed: 11/22/2022]
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13
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Malhotra K, Alder NN. Advances in the use of nanoscale bilayers to study membrane protein structure and function. Biotechnol Genet Eng Rev 2015; 30:79-93. [PMID: 25023464 DOI: 10.1080/02648725.2014.921502] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Within the last decade, nanoscale lipid bilayers have emerged as powerful experimental systems in the analysis of membrane proteins (MPs) for both basic and applied research. These discoidal lipid lamellae are stabilized by annuli of specially engineered amphipathic polypeptides (nanodiscs) or polymers (SMALPs/Lipodisqs®). As biomembrane mimetics, they are well suited for the reconstitution of MPs within a controlled lipid environment. Moreover, because they are water-soluble, they are amenable to solution-based biochemical and biophysical experimentation. Hence, due to their solubility, size, stability, and monodispersity, nanoscale lipid bilayers offer technical advantages over more traditional MP analytic approaches such as detergent solubilization and reconstitution into lipid vesicles. In this article, we review some of the most recent advances in the synthesis of polypeptide- and polymer-bound nanoscale lipid bilayers and their application in the study of MP structure and function.
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Affiliation(s)
- Ketan Malhotra
- a Department of Molecular and Cell Biology , University of Connecticut , Storrs , CT 06269 , USA
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14
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Boudker O, Oh S. Isothermal titration calorimetry of ion-coupled membrane transporters. Methods 2015; 76:171-182. [PMID: 25676707 PMCID: PMC4912014 DOI: 10.1016/j.ymeth.2015.01.012] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2014] [Revised: 01/20/2015] [Accepted: 01/21/2015] [Indexed: 11/17/2022] Open
Abstract
Binding of ligands, ranging from proteins to ions, to membrane proteins is associated with absorption or release of heat that can be detected by isothermal titration calorimetry (ITC). Such measurements not only provide binding affinities but also afford direct access to thermodynamic parameters of binding--enthalpy, entropy and heat capacity. These parameters can be interpreted in a structural context, allow discrimination between different binding mechanisms and guide drug design. In this review, we introduce advantages and limitations of ITC as a methodology to study molecular interactions of membrane proteins. We further describe case studies where ITC was used to analyze thermodynamic linkage between ions and substrates in ion-coupled transporters. Similar type of linkage analysis will likely be applicable to a wide range of transporters, channels, and receptors.
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Affiliation(s)
- Olga Boudker
- Department of Physiology & Biophysics, Weill Cornell Medical College, New York 10021, USA.
| | - SeCheol Oh
- Department of Physiology & Biophysics, Weill Cornell Medical College, New York 10021, USA.
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15
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Lantez V, Nikolaidis I, Rechenmann M, Vernet T, Noirclerc-Savoye M. Rapid automated detergent screening for the solubilization and purification of membrane proteins and complexes. Eng Life Sci 2015. [DOI: 10.1002/elsc.201400187] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Affiliation(s)
- Violaine Lantez
- Université Grenoble Alpes, IBS; Grenoble France
- CEA, IBS; Grenoble France
- CNRS, IBS; Grenoble France
| | - Ioulia Nikolaidis
- Université Grenoble Alpes, IBS; Grenoble France
- CEA, IBS; Grenoble France
- CNRS, IBS; Grenoble France
- Department of Biochemistry of Membranes; Bijvoet Center for Biomolecular Research, Utrecht University; The Netherlands
| | - Mathias Rechenmann
- Université Grenoble Alpes, IBS; Grenoble France
- CEA, IBS; Grenoble France
- CNRS, IBS; Grenoble France
| | - Thierry Vernet
- Université Grenoble Alpes, IBS; Grenoble France
- CEA, IBS; Grenoble France
- CNRS, IBS; Grenoble France
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