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Magee T, Henderson P, Baker A, Postis V, Muench S. A Tribute to Stephen Allan Baldwin. Mol Membr Biol 2015; 32:33-4. [PMID: 26094888 DOI: 10.3109/09687688.2015.1031834] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Affiliation(s)
- Tony Magee
- Editor-in-Chief of Molecular Membrane Biology
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Postis V, Rawson S, Mitchell JK, Lee SC, Parslow RA, Dafforn TR, Baldwin SA, Muench SP. The use of SMALPs as a novel membrane protein scaffold for structure study by negative stain electron microscopy. Biochim Biophys Acta 2014; 1848:496-501. [PMID: 25450810 PMCID: PMC4331651 DOI: 10.1016/j.bbamem.2014.10.018] [Citation(s) in RCA: 124] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/19/2014] [Revised: 10/06/2014] [Accepted: 10/15/2014] [Indexed: 12/17/2022]
Abstract
Despite the great progress recently made in resolving their structures, investigation of the structural biology of membrane proteins still presents major challenges. Even with new technical advances such as lipidic cubic phase crystallisation, obtaining well-ordered crystals remains a significant hurdle in membrane protein X-ray crystallographic studies. As an alternative, electron microscopy has been shown to be capable of resolving > 3.5 Å resolution detail in membrane proteins of modest (~ 300 kDa) size, without the need for crystals. However, the conventional use of detergents for either approach presents several issues, including the possible effects on structure of removing the proteins from their natural membrane environment. As an alternative, it has recently been demonstrated that membrane proteins can be effectively isolated, in the absence of detergents, using a styrene maleic acid co-polymer (SMA). This approach yields SMA lipid particles (SMALPs) in which the membrane proteins are surrounded by a small disk of lipid bilayer encircled by polymer. Here we use the Escherichia coli secondary transporter AcrB as a model membrane protein to demonstrate how a SMALP scaffold can be used to visualise membrane proteins, embedded in a near-native lipid environment, by negative stain electron microscopy, yielding structures at a modest resolution in a short (days) timeframe. Moreover, we show that AcrB within a SMALP scaffold is significantly more active than the equivalent DDM stabilised form. The advantages of SMALP scaffolds within electron microscopy are discussed and we conclude that they may prove to be an important tool in studying membrane protein structure and function. Maintaining membrane proteins in a native-like environment is difficult. SMALP scaffolds efficiently extract AcrB from the membrane. We show SMALP scaffolds to be a robust tool for rapid structural analysis by EM.
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Affiliation(s)
- Vincent Postis
- School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, LS2 9JT, UK; Biomedicine Research Group, Faculty of Health and Social Sciences, Leeds Beckett University, LS1 3HE, UK
| | - Shaun Rawson
- School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, LS2 9JT, UK
| | - Jennifer K Mitchell
- School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, LS2 9JT, UK
| | - Sarah C Lee
- School of Biosciences, University of Birmingham, Birmingham, Edgbaston B15 2TT, UK
| | - Rosemary A Parslow
- School of Biosciences, University of Birmingham, Birmingham, Edgbaston B15 2TT, UK
| | - Tim R Dafforn
- School of Biosciences, University of Birmingham, Birmingham, Edgbaston B15 2TT, UK
| | - Stephen A Baldwin
- School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, LS2 9JT, UK
| | - Stephen P Muench
- School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, LS2 9JT, UK.
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Yamashita M, Shepherd M, Booth WI, Xie H, Postis V, Nyathi Y, Tzokov SB, Poole RK, Baldwin SA, Bullough PA. Structure and function of the bacterial heterodimeric ABC transporter CydDC: stimulation of ATPase activity by thiol and heme compounds. J Biol Chem 2014; 289:23177-23188. [PMID: 24958725 PMCID: PMC4132815 DOI: 10.1074/jbc.m114.590414] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
In Escherichia coli, the biogenesis of both cytochrome bd-type quinol oxidases and periplasmic cytochromes requires the ATP-binding cassette-type cysteine/GSH transporter, CydDC. Recombinant CydDC was purified as a heterodimer and found to be an active ATPase both in soluble form with detergent and when reconstituted into a lipid environment. Two-dimensional crystals of CydDC were analyzed by electron cryomicroscopy, and the protein was shown to be made up of two non-identical domains corresponding to the putative CydD and CydC subunits, with dimensions characteristic of other ATP-binding cassette transporters. CydDC binds heme b. Detergent-solubilized CydDC appears to adopt at least two structural states, each associated with a characteristic level of bound heme. The purified protein in detergent showed a weak basal ATPase activity (approximately 100 nmol Pi/min/mg) that was stimulated ∼3-fold by various thiol compounds, suggesting that CydDC could act as a thiol transporter. The presence of heme (either intrinsic or added in the form of hemin) led to a further enhancement of thiol-stimulated ATPase activity, although a large excess of heme inhibited activity. Similar responses of the ATPase activity were observed with CydDC reconstituted into E. coli lipids. These results suggest that heme may have a regulatory role in CydDC-mediated transmembrane thiol transport.
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Affiliation(s)
- Masao Yamashita
- Krebs Institute for Biomolecular Research, Department of Molecular Biology and Biotechnology, The University of Sheffield, Sheffield S10 2TN, United Kingdom and
| | - Mark Shepherd
- Krebs Institute for Biomolecular Research, Department of Molecular Biology and Biotechnology, The University of Sheffield, Sheffield S10 2TN, United Kingdom and
| | - Wesley I Booth
- Krebs Institute for Biomolecular Research, Department of Molecular Biology and Biotechnology, The University of Sheffield, Sheffield S10 2TN, United Kingdom and
| | - Hao Xie
- School of Biomedical Sciences, The Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Vincent Postis
- School of Biomedical Sciences, The Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Yvonne Nyathi
- School of Biomedical Sciences, The Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Svetomir B Tzokov
- Krebs Institute for Biomolecular Research, Department of Molecular Biology and Biotechnology, The University of Sheffield, Sheffield S10 2TN, United Kingdom and
| | - Robert K Poole
- Krebs Institute for Biomolecular Research, Department of Molecular Biology and Biotechnology, The University of Sheffield, Sheffield S10 2TN, United Kingdom and
| | - Stephen A Baldwin
- School of Biomedical Sciences, The Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Per A Bullough
- Krebs Institute for Biomolecular Research, Department of Molecular Biology and Biotechnology, The University of Sheffield, Sheffield S10 2TN, United Kingdom and.
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Gutmann DAP, Mizohata E, Newstead S, Ferrandon S, Postis V, Xia X, Henderson PJF, van Veen HW, Byrne B. A high-throughput method for membrane protein solubility screening: the ultracentrifugation dispersity sedimentation assay. Protein Sci 2007; 16:1422-8. [PMID: 17567744 PMCID: PMC2206705 DOI: 10.1110/ps.072759907] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
One key to successful crystallization of membrane proteins is the identification of detergents that maintain the protein in a soluble, monodispersed state. Because of their hydrophobic nature, membrane proteins are particularly prone to forming insoluble aggregates over time. This nonspecific aggregation of the molecules reduces the likelihood of the regular association of the protein molecules essential for crystal lattice formation. Critical buffer components affecting the aggregation of membrane proteins include detergent choice, salt concentration, and presence of glycerol. The optimization of these parameters is often a time- and protein-consuming process. Here we describe a novel ultracentrifugation dispersity sedimentation (UDS) assay in which ultracentrifugation of very small (5 microL) volumes of purified, soluble membrane protein is combined with SDS-PAGE analysis to rapidly assess the degree of protein aggregation. The results from the UDS method correlate very well with established methods like size-exclusion chromatography (SEC), while consuming considerably less protein. In addition, the UDS method allows rapid screening of detergents for membrane protein crystallization in a fraction of the time required by SEC. Here we use the UDS method in the identification of suitable detergents and buffer compositions for the crystallization of three recombinant prokaryotic membrane proteins. The implications of our results for membrane protein crystallization prescreening are discussed.
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Affiliation(s)
- Daniel A P Gutmann
- Membrane Protein Crystallography Group, Division of Molecular Biosciences, Imperial College London, UK
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Postis V, De Marcos Lousa C, Arnou B, Lauquin GJM, Trézéguet V. Subunits of the yeast mitochondrial ADP/ATP carrier: cooperation within the dimer. Biochemistry 2006; 44:14732-40. [PMID: 16274221 DOI: 10.1021/bi051648x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The mitochondrial ADP/ATP carrier, or Ancp, is a member of the mitochondrial carrier family (MCF). It exchanges ADP and ATP between matrix and intermembrane space. It is postulated from numerous experiments that the inactive Ancp bound to one of its inhibitors (CATR or BA) is a dimer, and it is inferred that the active unit is a dimer, too. However, the structure of beef Ancp bound to CATR obtained at high resolution is that of a monomer. To ascertain the dimeric organization of Ancp, we have constructed covalent tandem dimers of which one "subunit" (protomer) is the wild type and the other is inactive for ADP/ATP exchange. We have chosen either the op1 mutant or another member of the MCF, the phosphate carrier (Picp). Activities of the chimeras were first evaluated in vivo. The Ancp/op1 constructs exchange the adenine nucleotides. The Anc/Pic chimeras are considered as bifunctional forms since they exchange ADP and ATP and transport P(i) within the same cells. We have then controlled the fact that the chimeras are stable in vivo and in vitro. Proteinase K digestion showed that both protomers of Ancp/op1 have similar organization in the membrane. Analyses of kinetic properties indicated that protomers of Ancp/op1 chimeras crosstalk during the nucleotide exchange unlike those of Anc/Pic. However, full inhibition of phosphate uptake by CATR, a very specific inhibitor of Ancp, strongly suggests that the native functional unit of Ancp, and thus of Picp, is a dimer.
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Affiliation(s)
- Vincent Postis
- Laboratoire de Physiologie Moléculaire et Cellulaire, UMR 5095-Université de Bordeaux2-CNRS, IBGC, 1, rue Camille Saint-Saëns, 33077 Bordeaux Cedex, France
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De Marcos Lousa C, Trézéguet V, David C, Postis V, Arnou B, Pebay-Peyroula E, Brandolin G, Lauquin GJM. Valine 181 is critical for the nucleotide exchange activity of human mitochondrial ADP/ATP carriers in yeast. Biochemistry 2005; 44:4342-8. [PMID: 15766263 DOI: 10.1021/bi0475370] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We isolated yeast Saccharomyces cerevisiae cells transformed with one of the three human adenine nucleotide carrier genes (HANC) that exhibited higher growth capacity than previously observed. The HANC genes were isolated from these clones, and we identified two independent mutations of HANC that led to replacement of valine 181 located in the fourth transmembrane segment by methionine or phenylalanine. Tolerance of this position toward substitution with various amino acids was systematically investigated, and since HANC/V181M was among the most efficient in growth complementation, it was more extensively studied. Here we show that increased growth capacities were associated with higher ADP/ATP exchange activities and not with higher human carrier amount in yeast mitochondria. These results are discussed in the light of the bovine Ancp structure, that shares more than 90% amino acid identity with Hancps, and its interaction with the lipid environment.
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Affiliation(s)
- Carine De Marcos Lousa
- Laboratoire de Physiologie Moléculaire et Cellulaire, IBGC-CNRS, UMR 5095, 1 rue Camille Saint-Saëns, 33077 Bordeaux Cedex, France
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Zeman I, Schwimmer C, Postis V, Brandolin G, David C, Trézéguet V, Lauquin GJM. Four mutations in transmembrane domains of the mitochondrial ADP/ATP carrier increase resistance to bongkrekic acid. J Bioenerg Biomembr 2004; 35:243-56. [PMID: 13678275 DOI: 10.1023/a:1024611731860] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Two distinct conformations of the mitochondrial ADP/ATP carrier involved in the adenine nucleotide transport are called BA and CATR conformations, as they were distinguished by binding of specific inhibitors bongkrekic acid (BA) and carboxyatractyloside (CATR), respectively. To find out which amino acids are implicated in the transition between these two conformations, which occurs during transport, mutants of the Saccharomyces cerevisiae ADP/ATP carrier Anc2p responsible for resistance of yeast cells to BA were identified and characterized after in vivo chemical or UV mutagenesis. Only four different mutations could be identified in spite of a large number of mutants analyzed. They are located in the Anc2p transmembrane segments I (G30S), II (Y97C), III (L142S), and VI (G298S), and are independently enabling growth of cells in the presence of BA. The variant and wild-type Anc2p were produced practically to the same level in mitochondria, as evidenced by immunochemical analysis and by atractyloside binding experiments. ADP/ATP exchange mediated by Anc2p variants in isolated mitochondria was more efficient than that of the wild-type Anc2p in the presence of BA, confirming that BA resistance of the mutant cells was linked to the functional properties of the modified ADP/ATP carrier. These results suggest that resistance to BA is caused by alternate conformation of Anc2p due to appearance of Ser or Cys at specific positions. Different interactions of these residues with other amino acids and/or BA could prevent formation of stable inactive Anc2p . BA complex.
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Affiliation(s)
- Igor Zeman
- Department of Biochemistry, Faculty of Sciences, Comenius University, Mlynská dolina CH-1, 842 15 Bratislava, Slovakia
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