101
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Li XZ, Plésiat P, Nikaido H. The challenge of efflux-mediated antibiotic resistance in Gram-negative bacteria. Clin Microbiol Rev 2015; 28:337-418. [PMID: 25788514 PMCID: PMC4402952 DOI: 10.1128/cmr.00117-14] [Citation(s) in RCA: 899] [Impact Index Per Article: 99.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
The global emergence of multidrug-resistant Gram-negative bacteria is a growing threat to antibiotic therapy. The chromosomally encoded drug efflux mechanisms that are ubiquitous in these bacteria greatly contribute to antibiotic resistance and present a major challenge for antibiotic development. Multidrug pumps, particularly those represented by the clinically relevant AcrAB-TolC and Mex pumps of the resistance-nodulation-division (RND) superfamily, not only mediate intrinsic and acquired multidrug resistance (MDR) but also are involved in other functions, including the bacterial stress response and pathogenicity. Additionally, efflux pumps interact synergistically with other resistance mechanisms (e.g., with the outer membrane permeability barrier) to increase resistance levels. Since the discovery of RND pumps in the early 1990s, remarkable scientific and technological advances have allowed for an in-depth understanding of the structural and biochemical basis, substrate profiles, molecular regulation, and inhibition of MDR pumps. However, the development of clinically useful efflux pump inhibitors and/or new antibiotics that can bypass pump effects continues to be a challenge. Plasmid-borne efflux pump genes (including those for RND pumps) have increasingly been identified. This article highlights the recent progress obtained for organisms of clinical significance, together with methodological considerations for the characterization of MDR pumps.
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Affiliation(s)
- Xian-Zhi Li
- Human Safety Division, Veterinary Drugs Directorate, Health Products and Food Branch, Health Canada, Ottawa, Ontario, Canada
| | - Patrick Plésiat
- Laboratoire de Bactériologie, Faculté de Médecine-Pharmacie, Centre Hospitalier Régional Universitaire, Université de Franche-Comté, Besançon, France
| | - Hiroshi Nikaido
- Department of Molecular and Cell Biology, University of California, Berkeley, California, USA
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102
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Abstract
Since determination of the myoglobin structure in 1957, X-ray crystallography, as the anchoring tool of structural biology, has played an instrumental role in deciphering the secrets of life. Knowledge gained through X-ray crystallography has fundamentally advanced our views on cellular processes and greatly facilitated development of modern medicine. In this brief narrative, I describe my personal understanding of the evolution of structural biology through X-ray crystallography-using as examples mechanistic understanding of protein kinases and integral membrane proteins-and comment on the impact of technological development and outlook of X-ray crystallography.
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Affiliation(s)
- Yigong Shi
- Center for Structural Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences and School of Medicine, Tsinghua University, Beijing 100084, China.
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103
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Madej MG. Comparative Sequence-Function Analysis of the Major Facilitator Superfamily: The "Mix-and-Match" Method. Methods Enzymol 2015; 557:521-49. [PMID: 25950980 DOI: 10.1016/bs.mie.2014.12.015] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The major facilitator superfamily (MFS) is a diverse group of secondary transporters with members found in all kingdoms of life. The paradigm for MFS is the lactose permease (LacY) of Escherichia coli, which has been the test bed for the development of many methods applied for the analysis of transport proteins. X-ray structures of an inward-facing conformation and the most recent structure of an almost occluded conformation confirm many conclusions from previous studies. One fundamentally important problem for understanding the mechanism of secondary active transport is the identification and physical localization of residues involved in substrate and H(+) binding. This information is exceptionally difficult to obtain with the MFS because of the broad sequence diversity among the members. The increasing number of solved MFS structures has led to the recognition of a common feature: inverted structure-repeat, formed by fused triple-helix domains with opposite orientation in the membrane. The presented method here exploits this feature to predict functionally homologous positions of known relevant positions in LacY. The triple-helix motifs are aligned in combinatorial fashion so as to detect substrate and H(+)-binding sites in symporters that transport substrates, ranging from simple ions like phosphate to more complex disaccharides.
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Affiliation(s)
- M Gregor Madej
- Department of Physiology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, USA.
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104
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McDermott JE, Bruillard P, Overall CC, Gosink L, Lindemann SR. Prediction of multi-drug resistance transporters using a novel sequence analysis method. F1000Res 2015; 4:60. [PMID: 26913187 PMCID: PMC4743146 DOI: 10.12688/f1000research.6200.2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 05/18/2015] [Indexed: 11/20/2022] Open
Abstract
There are many examples of groups of proteins that have similar function, but the determinants of functional specificity may be hidden by lack of sequence similarity, or by large groups of similar sequences with different functions. Transporters are one such protein group in that the general function, transport, can be easily inferred from the sequence, but the substrate specificity can be impossible to predict from sequence with current methods. In this paper we describe a linguistic-based approach to identify functional patterns from groups of unaligned protein sequences and its application to predict multi-drug resistance transporters (MDRs) from bacteria. We first show that our method can recreate known patterns from PROSITE for several motifs from unaligned sequences. We then show that the method, MDRpred, can predict MDRs with greater accuracy and positive predictive value than a collection of currently available family-based models from the Pfam database. Finally, we apply MDRpred to a large collection of protein sequences from an environmental microbiome study to make novel predictions about drug resistance in a potential environmental reservoir.
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Affiliation(s)
- Jason E. McDermott
- Biological Sciences, Pacific Northwest National Laboratory, Washington, WA, 99352, USA
- Department of Molecular Microbiology and Immunology, Oregon Health & Science University, Portland, OR, 97239, USA
| | - Paul Bruillard
- National Security Divisions, Pacific Northwest National Laboratory, Washington, WA, 99352, USA
| | | | - Luke Gosink
- National Security Divisions, Pacific Northwest National Laboratory, Washington, WA, 99352, USA
| | - Stephen R. Lindemann
- Biological Sciences, Pacific Northwest National Laboratory, Washington, WA, 99352, USA
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105
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McDermott JE, Bruillard P, Overall CC, Gosink L, Lindemann SR. Prediction of multi-drug resistance transporters using a novel sequence analysis method. F1000Res 2015; 4:60. [PMID: 26913187 PMCID: PMC4743146 DOI: 10.12688/f1000research.6200.1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 03/05/2015] [Indexed: 03/26/2024] Open
Abstract
There are many examples of groups of proteins that have similar function, but the determinants of functional specificity may be hidden by lack of sequence similarity, or by large groups of similar sequences with different functions. Transporters are one such protein group in that the general function, transport, can be easily inferred from the sequence, but the substrate specificity can be impossible to predict from sequence with current methods. In this paper we describe a linguistic-based approach to identify functional patterns from groups of unaligned protein sequences and its application to predict multi-drug resistance transporters (MDRs) from bacteria. We first show that our method can recreate known patterns from PROSITE for several motifs from unaligned sequences. We then show that the method, MDRpred, can predict MDRs with greater accuracy and positive predictive value than a collection of currently available family-based models from the Pfam database. Finally, we apply MDRpred to a large collection of protein sequences from an environmental microbiome study to make novel predictions about drug resistance in a potential environmental reservoir.
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Affiliation(s)
- Jason E. McDermott
- Biological Sciences, Pacific Northwest National Laboratory, Washington, WA, 99352, USA
- Department of Molecular Microbiology and Immunology, Oregon Health & Science University, Portland, OR, 97239, USA
| | - Paul Bruillard
- National Security Divisions, Pacific Northwest National Laboratory, Washington, WA, 99352, USA
| | | | - Luke Gosink
- National Security Divisions, Pacific Northwest National Laboratory, Washington, WA, 99352, USA
| | - Stephen R. Lindemann
- Biological Sciences, Pacific Northwest National Laboratory, Washington, WA, 99352, USA
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106
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Purification of a Multidrug Resistance Transporter for Crystallization Studies. Antibiotics (Basel) 2015; 4:113-35. [PMID: 27025617 PMCID: PMC4790320 DOI: 10.3390/antibiotics4010113] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2015] [Revised: 02/23/2015] [Accepted: 02/25/2015] [Indexed: 01/12/2023] Open
Abstract
Crystallization of integral membrane proteins is a challenging field and much effort has been invested in optimizing the overexpression and purification steps needed to obtain milligram amounts of pure, stable, monodisperse protein sample for crystallography studies. Our current work involves the structural and functional characterization of the Escherichia coli multidrug resistance transporter MdtM, a member of the major facilitator superfamily (MFS). Here we present a protocol for isolation of MdtM to increase yields of recombinant protein to the milligram quantities necessary for pursuit of structural studies using X-ray crystallography. Purification of MdtM was enhanced by introduction of an elongated His-tag, followed by identification and subsequent removal of chaperonin contamination. For crystallization trials of MdtM, detergent screening using size exclusion chromatography determined that decylmaltoside (DM) was the shortest-chain detergent that maintained the protein in a stable, monodispersed state. Crystallization trials of MdtM performed using the hanging-drop diffusion method with commercially available crystallization screens yielded 3D protein crystals under several different conditions. We contend that the purification protocol described here may be employed for production of high-quality protein of other multidrug efflux members of the MFS, a ubiquitous, physiologically and clinically important class of membrane transporters.
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107
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Du D, van Veen HW, Luisi BF. Assembly and operation of bacterial tripartite multidrug efflux pumps. Trends Microbiol 2015; 23:311-9. [PMID: 25728476 DOI: 10.1016/j.tim.2015.01.010] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2014] [Revised: 01/13/2015] [Accepted: 01/22/2015] [Indexed: 01/21/2023]
Abstract
Microorganisms encode several classes of transmembrane pumps that can expel an enormous range of toxic substances, thereby improving their fitness in harsh environments and contributing to resistance against antimicrobial agents. In Gram-negative bacteria these pumps can take the form of tripartite assemblies that actively efflux drugs and other harmful compounds across the cell envelope. We describe recent structural and functional data that have provided insights into the transport mechanisms of these intricate molecular machines.
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Affiliation(s)
- Dijun Du
- Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1GA, UK
| | - Hendrik W van Veen
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK
| | - Ben F Luisi
- Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1GA, UK.
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108
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Zhang Z, Wang R, Xie J. Mycobacterium smegmatis MSMEG_3705 Encodes a Selective Major Facilitator Superfamily Efflux Pump with Multiple Roles. Curr Microbiol 2015; 70:801-9. [DOI: 10.1007/s00284-015-0783-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2014] [Accepted: 12/15/2014] [Indexed: 11/30/2022]
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109
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Fowler PW, Orwick-Rydmark M, Radestock S, Solcan N, Dijkman PM, Lyons JA, Kwok J, Caffrey M, Watts A, Forrest LR, Newstead S. Gating topology of the proton-coupled oligopeptide symporters. Structure 2015; 23:290-301. [PMID: 25651061 PMCID: PMC4321885 DOI: 10.1016/j.str.2014.12.012] [Citation(s) in RCA: 82] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2014] [Revised: 11/21/2014] [Accepted: 12/03/2014] [Indexed: 01/10/2023]
Abstract
Proton-coupled oligopeptide transporters belong to the major facilitator superfamily (MFS) of membrane transporters. Recent crystal structures suggest the MFS fold facilitates transport through rearrangement of their two six-helix bundles around a central ligand binding site; how this is achieved, however, is poorly understood. Using modeling, molecular dynamics, crystallography, functional assays, and site-directed spin labeling combined with double electron-electron resonance (DEER) spectroscopy, we present a detailed study of the transport dynamics of two bacterial oligopeptide transporters, PepTSo and PepTSt. Our results identify several salt bridges that stabilize outward-facing conformations and we show that, for all the current structures of MFS transporters, the first two helices of each of the four inverted-topology repeat units form half of either the periplasmic or cytoplasmic gate and that these function cooperatively in a scissor-like motion to control access to the peptide binding site during transport.
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Affiliation(s)
- Philip W Fowler
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK.
| | | | - Sebastian Radestock
- Max Planck Institute of Biophysics, Max-von-Laue-Straße 3, Frankfurt am Main, Germany
| | - Nicolae Solcan
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Patricia M Dijkman
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Joseph A Lyons
- School of Biochemistry and Immunology, Trinity College Dublin, Dublin 2, Ireland
| | - Jane Kwok
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Martin Caffrey
- School of Biochemistry and Immunology, Trinity College Dublin, Dublin 2, Ireland
| | - Anthony Watts
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Lucy R Forrest
- Max Planck Institute of Biophysics, Max-von-Laue-Straße 3, Frankfurt am Main, Germany
| | - Simon Newstead
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK.
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110
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Fischer J, Kleinau G, Müller A, Kühnen P, Zwanziger D, Kinne A, Rehders M, Moeller LC, Führer D, Grüters A, Krude H, Brix K, Biebermann H. Modulation of monocarboxylate transporter 8 oligomerization by specific pathogenic mutations. J Mol Endocrinol 2015; 54:39-50. [PMID: 25527620 DOI: 10.1530/jme-14-0272] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The monocarboxylate transporter 8 (MCT8) is a member of the major facilitator superfamily (MFS). These membrane-spanning proteins facilitate translocation of a variety of substrates, MCT8 specifically transports iodothyronines. Mutations in MCT8 are the underlying cause of severe X-linked psychomotor retardation. At the molecular level, such mutations led to deficiencies in substrate translocation due to reduced cell-surface expression, impaired substrate binding, or decreased substrate translocation capabilities. However, the causal relationships between genotypes, molecular features of mutated MCT8, and patient characteristics have not yet been comprehensively deciphered. We investigated the relationship between pathogenic mutants of MCT8 and their capacity to form dimers (presumably oligomeric structures) as a potential regulatory parameter of the transport function of MCT8. Fourteen pathogenic variants of MCT8 were investigated in vitro with respect to their capacity to form oligomers. Particular mutations close to the substrate translocation channel (S194F, A224T, L434W, and R445C) were found to inhibit dimerization of MCT8. This finding is in contrast to those for other transporters or transmembrane proteins, in which substitutions predominantly at the outer-surface inhibit oligomerization. Moreover, specific mutations of MCT8 located in transmembrane helix 2 (del230F, V235M, and ins236V) increased the capacity of MCT8 variants to dimerize. We analyzed the localization of MCT8 dimers in a cellular context, demonstrating differences in MCT8 dimer formation and distribution. In summary, our results add a new link between the functions (substrate transport) and protein organization (dimerization) of MCT8, and might be of relevance for other members of the MFS. Finally, the findings are discussed in relationship to functional data combined with structural-mechanistical insights into MCT8.
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Affiliation(s)
- Jana Fischer
- Institut für Experimentelle Pädiatrische EndokrinologieCharité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, GermanyLeibniz-Institut für Molekulare PharmakologieBerlin, GermanyUniversitätsklinikum EssenKlinik für Endokrinologie und Stoffwechselerkrankungen, Essen, GermanyJacobs University BremenBremen, Germany
| | - Gunnar Kleinau
- Institut für Experimentelle Pädiatrische EndokrinologieCharité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, GermanyLeibniz-Institut für Molekulare PharmakologieBerlin, GermanyUniversitätsklinikum EssenKlinik für Endokrinologie und Stoffwechselerkrankungen, Essen, GermanyJacobs University BremenBremen, Germany
| | - Anne Müller
- Institut für Experimentelle Pädiatrische EndokrinologieCharité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, GermanyLeibniz-Institut für Molekulare PharmakologieBerlin, GermanyUniversitätsklinikum EssenKlinik für Endokrinologie und Stoffwechselerkrankungen, Essen, GermanyJacobs University BremenBremen, Germany
| | - Peter Kühnen
- Institut für Experimentelle Pädiatrische EndokrinologieCharité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, GermanyLeibniz-Institut für Molekulare PharmakologieBerlin, GermanyUniversitätsklinikum EssenKlinik für Endokrinologie und Stoffwechselerkrankungen, Essen, GermanyJacobs University BremenBremen, Germany
| | - Denise Zwanziger
- Institut für Experimentelle Pädiatrische EndokrinologieCharité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, GermanyLeibniz-Institut für Molekulare PharmakologieBerlin, GermanyUniversitätsklinikum EssenKlinik für Endokrinologie und Stoffwechselerkrankungen, Essen, GermanyJacobs University BremenBremen, Germany
| | - Anita Kinne
- Institut für Experimentelle Pädiatrische EndokrinologieCharité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, GermanyLeibniz-Institut für Molekulare PharmakologieBerlin, GermanyUniversitätsklinikum EssenKlinik für Endokrinologie und Stoffwechselerkrankungen, Essen, GermanyJacobs University BremenBremen, Germany
| | - Maren Rehders
- Institut für Experimentelle Pädiatrische EndokrinologieCharité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, GermanyLeibniz-Institut für Molekulare PharmakologieBerlin, GermanyUniversitätsklinikum EssenKlinik für Endokrinologie und Stoffwechselerkrankungen, Essen, GermanyJacobs University BremenBremen, Germany
| | - Lars C Moeller
- Institut für Experimentelle Pädiatrische EndokrinologieCharité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, GermanyLeibniz-Institut für Molekulare PharmakologieBerlin, GermanyUniversitätsklinikum EssenKlinik für Endokrinologie und Stoffwechselerkrankungen, Essen, GermanyJacobs University BremenBremen, Germany
| | - Dagmar Führer
- Institut für Experimentelle Pädiatrische EndokrinologieCharité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, GermanyLeibniz-Institut für Molekulare PharmakologieBerlin, GermanyUniversitätsklinikum EssenKlinik für Endokrinologie und Stoffwechselerkrankungen, Essen, GermanyJacobs University BremenBremen, Germany
| | - Annette Grüters
- Institut für Experimentelle Pädiatrische EndokrinologieCharité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, GermanyLeibniz-Institut für Molekulare PharmakologieBerlin, GermanyUniversitätsklinikum EssenKlinik für Endokrinologie und Stoffwechselerkrankungen, Essen, GermanyJacobs University BremenBremen, Germany
| | - Heiko Krude
- Institut für Experimentelle Pädiatrische EndokrinologieCharité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, GermanyLeibniz-Institut für Molekulare PharmakologieBerlin, GermanyUniversitätsklinikum EssenKlinik für Endokrinologie und Stoffwechselerkrankungen, Essen, GermanyJacobs University BremenBremen, Germany
| | - Klaudia Brix
- Institut für Experimentelle Pädiatrische EndokrinologieCharité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, GermanyLeibniz-Institut für Molekulare PharmakologieBerlin, GermanyUniversitätsklinikum EssenKlinik für Endokrinologie und Stoffwechselerkrankungen, Essen, GermanyJacobs University BremenBremen, Germany
| | - Heike Biebermann
- Institut für Experimentelle Pädiatrische EndokrinologieCharité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, GermanyLeibniz-Institut für Molekulare PharmakologieBerlin, GermanyUniversitätsklinikum EssenKlinik für Endokrinologie und Stoffwechselerkrankungen, Essen, GermanyJacobs University BremenBremen, Germany
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111
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Andersen JL, He GX, Kakarla P, K C R, Kumar S, Lakra WS, Mukherjee MM, Ranaweera I, Shrestha U, Tran T, Varela MF. Multidrug efflux pumps from Enterobacteriaceae, Vibrio cholerae and Staphylococcus aureus bacterial food pathogens. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2015; 12:1487-547. [PMID: 25635914 PMCID: PMC4344678 DOI: 10.3390/ijerph120201487] [Citation(s) in RCA: 85] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/16/2014] [Accepted: 01/15/2015] [Indexed: 02/07/2023]
Abstract
Foodborne illnesses caused by bacterial microorganisms are common worldwide and constitute a serious public health concern. In particular, microorganisms belonging to the Enterobacteriaceae and Vibrionaceae families of Gram-negative bacteria, and to the Staphylococcus genus of Gram-positive bacteria are important causative agents of food poisoning and infection in the gastrointestinal tract of humans. Recently, variants of these bacteria have developed resistance to medically important chemotherapeutic agents. Multidrug resistant Escherichia coli, Salmonella enterica, Vibrio cholerae, Enterobacter spp., and Staphylococcus aureus are becoming increasingly recalcitrant to clinical treatment in human patients. Of the various bacterial resistance mechanisms against antimicrobial agents, multidrug efflux pumps comprise a major cause of multiple drug resistance. These multidrug efflux pump systems reside in the biological membrane of the bacteria and actively extrude antimicrobial agents from bacterial cells. This review article summarizes the evolution of these bacterial drug efflux pump systems from a molecular biological standpoint and provides a framework for future work aimed at reducing the conditions that foster dissemination of these multidrug resistant causative agents through human populations.
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Affiliation(s)
- Jody L Andersen
- Department of Biology, Eastern New Mexico University, Portales, NM 88130, USA.
| | - Gui-Xin He
- Department of Clinical Laboratory and Nutritional Sciences, University of Massachusetts Lowell, Lowell, MA 01854, USA.
| | - Prathusha Kakarla
- Department of Biology, Eastern New Mexico University, Portales, NM 88130, USA.
| | - Ranjana K C
- Department of Biology, Eastern New Mexico University, Portales, NM 88130, USA.
| | - Sanath Kumar
- QC Laboratory, Harvest and Post-Harvest Technology Division, Central Institute of Fisheries Education (CIFE), Seven Bungalows, Versova, Andheri (W), Mumbai 400061, India.
| | - Wazir Singh Lakra
- QC Laboratory, Harvest and Post-Harvest Technology Division, Central Institute of Fisheries Education (CIFE), Seven Bungalows, Versova, Andheri (W), Mumbai 400061, India.
| | - Mun Mun Mukherjee
- Department of Biology, Eastern New Mexico University, Portales, NM 88130, USA.
| | - Indrika Ranaweera
- Department of Biology, Eastern New Mexico University, Portales, NM 88130, USA.
| | - Ugina Shrestha
- Department of Biology, Eastern New Mexico University, Portales, NM 88130, USA.
| | - Thuy Tran
- Department of Clinical Laboratory and Nutritional Sciences, University of Massachusetts Lowell, Lowell, MA 01854, USA.
| | - Manuel F Varela
- Department of Biology, Eastern New Mexico University, Portales, NM 88130, USA.
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112
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Saidijam M, Patching SG. Amino acid composition analysis of secondary transport proteins from Escherichia coli with relation to functional classification, ligand specificity and structure. J Biomol Struct Dyn 2015; 33:2205-20. [DOI: 10.1080/07391102.2014.998283] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Affiliation(s)
- Massoud Saidijam
- Department of Molecular Medicine and Genetics, Research Centre for Molecular Medicine, School of Medicine, Hamadan University of Medical Sciences , Hamadan, Iran
| | - Simon G. Patching
- Department of Molecular Medicine and Genetics, Research Centre for Molecular Medicine, School of Medicine, Hamadan University of Medical Sciences , Hamadan, Iran
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113
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Shaheen A, Ismat F, Iqbal M, Haque A, De Zorzi R, Mirza O, Walz T, Rahman M. Characterization of putative multidrug resistance transporters of the major facilitator-superfamily expressed in Salmonella Typhi. J Infect Chemother 2015; 21:357-62. [PMID: 25724589 DOI: 10.1016/j.jiac.2015.01.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2014] [Revised: 12/03/2014] [Accepted: 01/02/2015] [Indexed: 01/11/2023]
Abstract
Multidrug resistance mediated by efflux pumps is a well-known phenomenon in infectious bacteria. Although much work has been carried out to characterize multidrug efflux pumps in Gram-negative and Gram-positive bacteria, such information is still lacking for many deadly pathogens. The aim of this study was to gain insight into the substrate specificity of previously uncharacterized transporters of Salmonella Typhi to identify their role in the development of multidrug resistance. S. Typhi genes encoding putative members of the major facilitator superfamily were cloned and expressed in the drug-hypersensitive Escherichia coli strain KAM42, and tested for transport of 25 antibacterial compounds, including representative antibiotics of various classes, antiseptics, dyes and detergents. Of the 15 tested putative transporters, STY0901, STY2458 and STY4874 exhibited a drug-resistance phenotype. Among these, STY4874 conferred resistance to at least ten of the tested antimicrobials: ciprofloxacin, norfloxacin, levofloxacin, kanamycin, streptomycin, gentamycin, nalidixic acid, chloramphenicol, ethidium bromide, and acriflavine, including fluoroquinolone antibiotics, which were drugs of choice to treat S. Typhi infections. Cell-based functional studies using ethidium bromide and acriflavine showed that STY4874 functions as a H(+)-dependent exporter. These results suggest that STY4874 may be an important drug target, which can now be tested by studying the susceptibility of a STY4874-deficient S. Typhi strain to antimicrobials.
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Affiliation(s)
- Aqsa Shaheen
- Drug Discovery and Structural Biology Group, Health Biotechnology Division, National Institute for Biotechnology and Genetic Engineering (NIBGE), Faisalabad, Pakistan; Pakistan Institute of Engineering and Applied Sciences, Islamabad, Pakistan; Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Fouzia Ismat
- Drug Discovery and Structural Biology Group, Health Biotechnology Division, National Institute for Biotechnology and Genetic Engineering (NIBGE), Faisalabad, Pakistan
| | - Mazhar Iqbal
- Drug Discovery and Structural Biology Group, Health Biotechnology Division, National Institute for Biotechnology and Genetic Engineering (NIBGE), Faisalabad, Pakistan; Pakistan Institute of Engineering and Applied Sciences, Islamabad, Pakistan
| | - Abdul Haque
- The University of Faisalabad, Faisalabad, Pakistan
| | - Rita De Zorzi
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA; Howard Hughes Medical Institute, Harvard Medical School, Boston, MA 02115, USA
| | - Osman Mirza
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Thomas Walz
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA; Howard Hughes Medical Institute, Harvard Medical School, Boston, MA 02115, USA
| | - Moazur Rahman
- Drug Discovery and Structural Biology Group, Health Biotechnology Division, National Institute for Biotechnology and Genetic Engineering (NIBGE), Faisalabad, Pakistan; Pakistan Institute of Engineering and Applied Sciences, Islamabad, Pakistan; Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA.
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114
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Ranaweera I, Shrestha U, Ranjana K, Kakarla P, Willmon TM, Hernandez AJ, Mukherjee MM, Barr SR, Varela MF. Structural comparison of bacterial multidrug efflux pumps of the major facilitator superfamily. TRENDS IN CELL & MOLECULAR BIOLOGY 2015; 10:131-140. [PMID: 27065631 PMCID: PMC4822553] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The biological membrane is an efficient barrier against water-soluble substances. Solute transporters circumvent this membrane barrier by transporting water-soluble solutes across the membrane to the other sides. These transport proteins are thus required for all living organisms. Microorganisms, such as bacteria, effectively exploit solute transporters to acquire useful nutrients for growth or to expel substances that are inhibitory to their growth. Overall, there are distinct types of related solute transporters that are grouped into families or superfamilies. Of these various transporters, the major facilitator superfamily (MFS) represents a very large and constantly growing group and are driven by solute- and ion-gradients, making them passive and secondary active transporters, respectively. Members of the major facilitator superfamily transport an extreme variety of structurally different substrates such as antimicrobial agents, amino acids, sugars, intermediary metabolites, ions, and other small molecules. Importantly, bacteria, especially pathogenic ones, have evolved multidrug efflux pumps which belong to the major facilitator superfamily. Furthermore, members of this important superfamily share similar primary sequences in the form of highly conserved sequence motifs that confer useful functional properties during transport. The transporters of the superfamily also share similarities in secondary structures, such as possessing 12- or 14-membrane spanning α-helices and the more recently described 3-helix structure repeat element, known as the MFS fold. The three-dimensional structures of bacterial multidrug efflux pumps have been determined for only a few members of the superfamily, all drug pumps of which are surprisingly from Escherichia coli. This review briefly summarizes the structural properties of the bacterial multidrug efflux pumps of the major facilitator superfamily in a comparative manner and provides future directions for study.
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Affiliation(s)
- Indrika Ranaweera
- Department of Biology, Eastern New Mexico University, Portales, NM 88130, USA
| | - Ugina Shrestha
- Department of Biology, Eastern New Mexico University, Portales, NM 88130, USA
| | - K.C. Ranjana
- Department of Biology, Eastern New Mexico University, Portales, NM 88130, USA
| | - Prathusha Kakarla
- Department of Biology, Eastern New Mexico University, Portales, NM 88130, USA
| | - T. Mark Willmon
- Department of Biology, Eastern New Mexico University, Portales, NM 88130, USA
| | | | - Mun Mun Mukherjee
- Department of Biology, Eastern New Mexico University, Portales, NM 88130, USA
| | - Sharla R. Barr
- Department of Biology, Eastern New Mexico University, Portales, NM 88130, USA
| | - Manuel F. Varela
- Department of Biology, Eastern New Mexico University, Portales, NM 88130, USA
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115
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Yaffe D, Vergara-Jaque A, Shuster Y, Listov D, Meena S, Singh SK, Forrest LR, Schuldiner S. Functionally important carboxyls in a bacterial homologue of the vesicular monoamine transporter (VMAT). J Biol Chem 2014; 289:34229-40. [PMID: 25336661 PMCID: PMC4256354 DOI: 10.1074/jbc.m114.607366] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2014] [Revised: 09/30/2014] [Indexed: 11/06/2022] Open
Abstract
Transporters essential for neurotransmission in mammalian organisms and bacterial multidrug transporters involved in antibiotic resistance are evolutionarily related. To understand in more detail the evolutionary aspects of the transformation of a bacterial multidrug transporter to a mammalian neurotransporter and to learn about mechanisms in a milieu amenable for structural and biochemical studies, we identified, cloned, and partially characterized bacterial homologues of the rat vesicular monoamine transporter (rVMAT2). We performed preliminary biochemical characterization of one of them, Brevibacillus brevis monoamine transporter (BbMAT), from the bacterium B. brevis. BbMAT shares substrates with rVMAT2 and transports them in exchange with >1H(+), like the mammalian transporter. Here we present a homology model of BbMAT that has the standard major facilitator superfamily fold; that is, with two domains of six transmembrane helices each, related by 2-fold pseudosymmetry whose axis runs normal to the membrane and between the two halves. The model predicts that four carboxyl residues, a histidine, and an arginine are located in the transmembrane segments. We show here that two of the carboxyls are conserved, equivalent to the corresponding ones in rVMAT2, and are essential for H(+)-coupled transport. We conclude that BbMAT provides an excellent experimental paradigm for the study of its mammalian counterparts and bacterial multidrug transporters.
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Affiliation(s)
- Dana Yaffe
- From the Department of Biological Chemistry, Alexander Silberman Institute of Life Sciences, Hebrew University, 91904 Jerusalem, Israel
| | - Ariela Vergara-Jaque
- the Computational Structural Biology Section, NINDS, National Institutes of Health, Bethesda, Maryland 20852, and
| | - Yonatan Shuster
- From the Department of Biological Chemistry, Alexander Silberman Institute of Life Sciences, Hebrew University, 91904 Jerusalem, Israel
| | - Dina Listov
- From the Department of Biological Chemistry, Alexander Silberman Institute of Life Sciences, Hebrew University, 91904 Jerusalem, Israel
| | - Sitaram Meena
- the Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut 06520
| | - Satinder K Singh
- the Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut 06520
| | - Lucy R Forrest
- the Computational Structural Biology Section, NINDS, National Institutes of Health, Bethesda, Maryland 20852, and
| | - Shimon Schuldiner
- From the Department of Biological Chemistry, Alexander Silberman Institute of Life Sciences, Hebrew University, 91904 Jerusalem, Israel,
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116
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Iyalomhe O, Herrick DZ, Cafiso DS, Maloney PC. Closure of the cytoplasmic gate formed by TM5 and TM11 during transport in the oxalate/formate exchanger from Oxalobacter formigenes. Biochemistry 2014; 53:7735-44. [PMID: 25409483 PMCID: PMC4270380 DOI: 10.1021/bi5012173] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
Abstract
![]()
OxlT, the oxalate/formate exchanger
of Oxalobacter
formigenes, is a member of the major facilitator superfamily
of transporters. In the present work, substrate (oxalate) was found
to enhance the reactivity of the cysteine mutant S336C on the cytoplasmic
end of helix 11 to methanethiosulfonate ethyl carboxylate. In addition,
S336C is found to spontaneously cross-link to S143C in TM5 in either
native or reconstituted membranes under conditions that support transport.
Continuous wave EPR measurements are consistent with this result and
indicate that positions 143 and 336 are in close proximity in the
presence of substrate. These two residues are localized within helix
interacting GxxxG-like motifs (G140LASG144 and
S336DIFG340) at the cytoplasmic poles of TM5
and TM11. Pulse EPR measurements were used to determine distances
and distance distributions across the cytoplasmic or periplasmic ends
of OxlT and were compared with the predictions of an inside-open homology
model. The data indicate that a significant population of transporter
is in an outside-open configuration in the presence of substrate;
however, each end of the transporter exhibits significant conformational
heterogeneity, where both inside-open and outside-open configurations
are present. These data indicate that TM5 and TM11, which form part
of the transport pathway, transiently close during transport and that
there is a conformational equilibrium between inside-open and outside-open
states of OxlT in the presence of substrate.
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Affiliation(s)
- Osigbemhe Iyalomhe
- Department of Physiology, The Johns Hopkins University, School of Medicine , 725 North Wolfe Street, Baltimore, Maryland 21205, United States
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117
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Blair JMA, Richmond GE, Piddock LJV. Multidrug efflux pumps in Gram-negative bacteria and their role in antibiotic resistance. Future Microbiol 2014; 9:1165-77. [DOI: 10.2217/fmb.14.66] [Citation(s) in RCA: 201] [Impact Index Per Article: 20.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
ABSTRACT Gram-negative bacteria express a plethora of efflux pumps that are capable of transporting structurally varied molecules, including antibiotics, out of the bacterial cell. This efflux lowers the intracellular antibiotic concentration, allowing bacteria to survive at higher antibiotic concentrations. Overexpression of some efflux pumps can cause clinically relevant levels of antibiotic resistance in Gram-negative pathogens. This review discusses the role of efflux in resistance of clinical isolates of Gram-negative bacteria, the regulatory mechanisms that control efflux pump expression, the recent advances in our understanding of efflux pump structure and how inhibition of efflux is a promising future strategy for tackling multidrug resistance in Gram-negative pathogens.
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Affiliation(s)
- Jessica MA Blair
- Antimicrobials Research Group, Institute of Microbiology & Infection, School of Immunity & Infection, College of Medical & Dental Sciences, University of Birmingham, Birmingham, B15 2TT, UK
| | - Grace E Richmond
- Antimicrobials Research Group, Institute of Microbiology & Infection, School of Immunity & Infection, College of Medical & Dental Sciences, University of Birmingham, Birmingham, B15 2TT, UK
| | - Laura JV Piddock
- Antimicrobials Research Group, Institute of Microbiology & Infection, School of Immunity & Infection, College of Medical & Dental Sciences, University of Birmingham, Birmingham, B15 2TT, UK
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118
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Jensen JM, Aduri NG, Prabhala BK, Jahnsen R, Franzyk H, Mirza O. Critical role of a conserved transmembrane lysine in substrate recognition by the proton-coupled oligopeptide transporter YjdL. Int J Biochem Cell Biol 2014; 55:311-7. [PMID: 25261786 DOI: 10.1016/j.biocel.2014.09.016] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2014] [Revised: 09/12/2014] [Accepted: 09/15/2014] [Indexed: 11/16/2022]
Abstract
Proton-coupled oligopeptide transporters (POTs) utilize an electrochemical proton gradient to accumulate peptides in the cytoplasm. Changing the highly conserved active-site Lys117 in the Escherichia coli POT YjdL to glutamine resulted in loss of ligand affinity as well as inability to distinguish between a dipeptide ligand and the corresponding dipeptide amide. The radically changed pH(Bulk) profiles of Lys117Gln and Lys117Arg mutants indicate an important role of Lys117 in facilitating protonation of the transporter; a notion that is supported by the close proximity of Lys117 to the conserved ExxERFxYY POT motif previously shown to be involved in proton translocation. These results point toward a novel dual role of Lys117 in direct or indirect interaction with both proton and peptide.
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Affiliation(s)
- Johanne M Jensen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Nanda G Aduri
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Bala K Prabhala
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Rasmus Jahnsen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Henrik Franzyk
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Osman Mirza
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
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119
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Function, Structure, and Evolution of the Major Facilitator Superfamily: The LacY Manifesto. ACTA ACUST UNITED AC 2014. [DOI: 10.1155/2014/523591] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The major facilitator superfamily (MFS) is a diverse group of secondary transporters with members found in all kingdoms of life. A paradigm for MFS is the lactose permease (LacY) of Escherichia coli, which couples the stoichiometric translocation of a galactopyranoside and an H+ across the cytoplasmic membrane. LacY has been the test bed for the development of many methods applied for the analysis of transport proteins. X-ray structures of an inward-facing conformation and the most recent structure of an almost occluded conformation confirm many conclusions from previous studies. Although structure models are critical, they are insufficient to explain the catalysis of transport. The clues to understanding transport are based on the principles of enzyme kinetics. Secondary transport is a dynamic process—static snapshots of X-ray crystallography describe it only partially. However, without structural information, the underlying chemistry is virtually impossible to conclude. A large body of biochemical/biophysical data derived from systematic studies of site-directed mutants in LacY suggests residues critically involved in the catalysis, and a working model for the symport mechanism that involves alternating access of the binding site is presented. The general concepts derived from the bacterial LacY are examined for their relevance to other MFS transporters.
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120
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The Structure and Function of OxlT, the Oxalate Transporter of Oxalobacter formigenes. J Membr Biol 2014; 248:641-50. [DOI: 10.1007/s00232-014-9728-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2014] [Accepted: 09/05/2014] [Indexed: 01/01/2023]
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121
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MemStar: A one-shotEscherichia coli-based approach for high-level bacterial membrane protein production. FEBS Lett 2014; 588:3761-9. [DOI: 10.1016/j.febslet.2014.08.025] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2014] [Revised: 08/21/2014] [Accepted: 08/21/2014] [Indexed: 01/22/2023]
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122
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Export of a single drug molecule in two transport cycles by a multidrug efflux pump. Nat Commun 2014; 5:4615. [DOI: 10.1038/ncomms5615] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2014] [Accepted: 07/07/2014] [Indexed: 11/08/2022] Open
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123
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Wisedchaisri G, Park MS, Iadanza MG, Zheng H, Gonen T. Proton-coupled sugar transport in the prototypical major facilitator superfamily protein XylE. Nat Commun 2014; 5:4521. [PMID: 25088546 PMCID: PMC4137407 DOI: 10.1038/ncomms5521] [Citation(s) in RCA: 106] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2014] [Accepted: 06/25/2014] [Indexed: 01/19/2023] Open
Abstract
The major facilitator superfamily (MFS) is the largest collection of structurally related membrane proteins that transport a wide array of substrates. The proton-coupled sugar transporter XylE is the first member of the MFS that has been structurally characterized in multiple transporting conformations, including both the outward and inward-facing states. Here we report the crystal structure of XylE in a new inward-facing open conformation, allowing us to visualize the rocker-switch movement of the N-domain against the C-domain during the transport cycle. Using molecular dynamics simulation, and functional transport assays, we describe the movement of XylE that facilitates sugar translocation across a lipid membrane and identify the likely candidate proton-coupling residues as the conserved Asp27 and Arg133. This study addresses the structural basis for proton-coupled substrate transport and release mechanism for the sugar porter family of proteins. Glucose transporters are a medically important class of membrane proteins often deregulated in diseases such as Type 2 diabetes. Here, Wisedchaisri et al. report the crystal structure of XylE in an inward-facing open conformation to provide a general mechanism of substrate transport for the sugar porter family of proteins.
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Affiliation(s)
- Goragot Wisedchaisri
- 1] Janelia Research Campus, Howard Hughes Medical Institute, 19700 Helix Drive, Ashburn, Virginia 20147, USA [2]
| | - Min-Sun Park
- 1] Janelia Research Campus, Howard Hughes Medical Institute, 19700 Helix Drive, Ashburn, Virginia 20147, USA [2]
| | - Matthew G Iadanza
- Janelia Research Campus, Howard Hughes Medical Institute, 19700 Helix Drive, Ashburn, Virginia 20147, USA
| | - Hongjin Zheng
- Janelia Research Campus, Howard Hughes Medical Institute, 19700 Helix Drive, Ashburn, Virginia 20147, USA
| | - Tamir Gonen
- Janelia Research Campus, Howard Hughes Medical Institute, 19700 Helix Drive, Ashburn, Virginia 20147, USA
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124
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Xu X, Chen J, Xu H, Li D. Role of a major facilitator superfamily transporter in adaptation capacity of Penicillium funiculosum under extreme acidic stress. Fungal Genet Biol 2014; 69:75-83. [DOI: 10.1016/j.fgb.2014.06.002] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2014] [Revised: 06/03/2014] [Accepted: 06/14/2014] [Indexed: 11/25/2022]
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125
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Wilson MR, Hou Z, Matherly LH. Substituted cysteine accessibility reveals a novel transmembrane 2-3 reentrant loop and functional role for transmembrane domain 2 in the human proton-coupled folate transporter. J Biol Chem 2014; 289:25287-95. [PMID: 25053408 DOI: 10.1074/jbc.m114.578252] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The proton-coupled folate transporter (PCFT) is a folate-proton symporter highly expressed in solid tumors that can selectively target cytotoxic antifolates to tumors under acidic microenvironment conditions. Predicted topology models for PCFT suggest that the loop domain between transmembrane domains (TMDs) 2 and 3 resides in the cytosol. Mutations involving Asp-109 or Arg-113 in the TMD2-3 loop result in loss of activity. By structural homology to other solute carriers, TMD2 may form part of the PCFT substrate binding domain. In this study we mutated the seven cysteine (Cys) residues of human PCFT to serine, creating Cys-less PCFT. Thirty-three single-Cys mutants spanning TMD2 and the TMD2-3 loop in a Cys-less PCFT background were transfected into PCFT-null HeLa cells. All 33 mutants were detected by Western blotting, and 28 were active for [(3)H]methotrexate uptake at pH 5.5. For the active residues, we performed pulldown assays with membrane-impermeable 2-aminoethyl methanethiosulfonate-biotin and streptavidin beads to determine their aqueous-accessibilities. Multiple residues in TMD2 and the TMD2-3 loop domain reacted with 2-aminoethyl methanethiosulfonate-biotin, establishing aqueous accessibilities. Pemetrexed pretreatment inhibited biotinylation of TMD2 mutants G93C and F94C, and biotinylation of these residues inhibited methotrexate transport activity. Our results suggest that the TMD 2-3 loop domain is aqueous-accessible and forms a novel reentrant loop structure. Residues in TMD2 form an aqueous transmembrane pathway for folate substrates, and Gly-93 and Phe-94 may contribute to a substrate binding domain. Characterization of PCFT structure is essential to understanding the transport mechanism including the critical determinants of substrate binding.
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Affiliation(s)
| | - Zhanjun Hou
- From the Department of Oncology and the Molecular Therapeutics Program, Barbara Ann Karmanos Cancer Institute, Detroit, Michigan 48201
| | - Larry H Matherly
- From the Department of Oncology and the Molecular Therapeutics Program, Barbara Ann Karmanos Cancer Institute, Detroit, Michigan 48201 Department of Pharmacology, Wayne State University School of Medicine and
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126
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Sun J, Deng Z, Yan A. Bacterial multidrug efflux pumps: mechanisms, physiology and pharmacological exploitations. Biochem Biophys Res Commun 2014; 453:254-67. [PMID: 24878531 DOI: 10.1016/j.bbrc.2014.05.090] [Citation(s) in RCA: 432] [Impact Index Per Article: 43.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2014] [Accepted: 05/20/2014] [Indexed: 01/11/2023]
Abstract
Multidrug resistance (MDR) refers to the capability of bacterial pathogens to withstand lethal doses of structurally diverse drugs which are capable of eradicating non-resistant strains. MDR has been identified as a major threat to the public health of human being by the World Health Organization (WHO). Among the four general mechanisms that cause antibiotic resistance including target alteration, drug inactivation, decreased permeability and increased efflux, drug extrusion by the multidrug efflux pumps serves as an important mechanism of MDR. Efflux pumps not only can expel a broad range of antibiotics owing to their poly-substrate specificity, but also drive the acquisition of additional resistance mechanisms by lowering intracellular antibiotic concentration and promoting mutation accumulation. Over-expression of multidrug efflux pumps have been increasingly found to be associated with clinically relevant drug resistance. On the other hand, accumulating evidence has suggested that efflux pumps also have physiological functions in bacteria and their expression is subject tight regulation in response to various of environmental and physiological signals. A comprehensive understanding of the mechanisms of drug extrusion, and regulation and physiological functions of efflux pumps is essential for the development of anti-resistance interventions. In this review, we summarize the development of these research areas in the recent decades and present the pharmacological exploitation of efflux pump inhibitors as a promising anti-drug resistance intervention.
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Affiliation(s)
- Jingjing Sun
- School of Biological Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong Special Administrative Region
| | - Ziqing Deng
- School of Biological Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong Special Administrative Region
| | - Aixin Yan
- School of Biological Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong Special Administrative Region.
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127
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Newstead S. Molecular insights into proton coupled peptide transport in the PTR family of oligopeptide transporters. Biochim Biophys Acta Gen Subj 2014; 1850:488-99. [PMID: 24859687 PMCID: PMC4331665 DOI: 10.1016/j.bbagen.2014.05.011] [Citation(s) in RCA: 83] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2014] [Revised: 05/12/2014] [Accepted: 05/13/2014] [Indexed: 12/15/2022]
Abstract
Background Cellular uptake of small peptides is an important physiological process mediated by the PTR family of proton-coupled peptide transporters. In bacteria peptides can be used as a source of amino acids and nitrogen. Similarly in humans peptide transport is the principle route for the uptake and retention of dietary protein in the form of short di- and tri-peptides for cellular metabolism. Scope of the review Recent crystal structures of bacterial PTR family transporters, combined with biochemical studies of transport have revealed key molecular details underpinning ligand promiscuity and the mechanism of proton-coupled transport within the family. Major conclusions Pairs of salt bridge interactions between transmembrane helices work in tandem to orchestrate alternating access transport within the PTR family. Key roles for residues conserved between bacterial and eukaryotic homologues suggest a conserved mechanism of peptide recognition and transport that in some cases has been subtly modified in individual species. General significance Physiological studies on PepT1 and PepT2, the mammalian members of this family, have identified these transporters as being responsible for the uptake of many pharmaceutically important drug molecules, including antibiotics and antiviral medications and demonstrated their promiscuity can be used for improving the oral bioavailability of poorly absorbed compounds. The insights gained from recent structural studies combined with previous physiological and biochemical analyses are rapidly advancing our understanding of this medically important transporter superfamily. This article is part of a Special Issue entitled Structural biochemistry and biophysics of membrane proteins. Crystal structures of PTR family transporters Identification of mechanistically important salt bridge interactions. Conservation of key functional residues between bacterial and mammalian homologues. High resolution structural information on peptide binding.
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Affiliation(s)
- Simon Newstead
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK
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128
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Paul S, Alegre KO, Holdsworth SR, Rice M, Brown JA, McVeigh P, Kelly SM, Law CJ. A single-component multidrug transporter of the major facilitator superfamily is part of a network that protects Escherichia coli from bile salt stress. Mol Microbiol 2014; 92:872-84. [PMID: 24684269 PMCID: PMC4235344 DOI: 10.1111/mmi.12597] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/26/2014] [Indexed: 01/16/2023]
Abstract
Resistance to high concentrations of bile salts in the human intestinal tract is vital for the survival of enteric bacteria such as Escherichia coli. Although the tripartite AcrAB-TolC efflux system plays a significant role in this resistance, it is purported that other efflux pumps must also be involved. We provide evidence from a comprehensive suite of experiments performed at two different pH values (7.2 and 6.0) that reflect pH conditions that E. coli may encounter in human gut that MdtM, a single-component multidrug resistance transporter of the major facilitator superfamily, functions in bile salt resistance in E. coli by catalysing secondary active transport of bile salts out of the cell cytoplasm. Furthermore, assays performed on a chromosomal ΔacrB mutant transformed with multicopy plasmid encoding MdtM suggested a functional synergism between the single-component MdtM transporter and the tripartite AcrAB-TolC system that results in a multiplicative effect on resistance. Substrate binding experiments performed on purified MdtM demonstrated that the transporter binds to cholate and deoxycholate with micromolar affinity, and transport assays performed on inverted vesicles confirmed the capacity of MdtM to catalyse electrogenic bile salt/H(+) antiport.
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Affiliation(s)
- Stephanie Paul
- Institute for Global Food Security, School of Biological Sciences, Medical Biology Centre, Queen's University Belfast, 97 Lisburn Road, Belfast, BT9 7BL, UK
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129
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Stelzl LS, Fowler PW, Sansom MS, Beckstein O. Flexible gates generate occluded intermediates in the transport cycle of LacY. J Mol Biol 2014; 426:735-51. [PMID: 24513108 PMCID: PMC3905165 DOI: 10.1016/j.jmb.2013.10.024] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2013] [Revised: 10/17/2013] [Accepted: 10/18/2013] [Indexed: 12/29/2022]
Abstract
The major facilitator superfamily (MFS) transporter lactose permease (LacY) alternates between cytoplasmic and periplasmic open conformations to co-transport a sugar molecule together with a proton across the plasma membrane. Indirect experimental evidence suggested the existence of an occluded transition intermediate of LacY, which would prevent leaking of the proton gradient. As no experimental structure is known, the conformational transition is not fully understood in atomic detail. We simulated transition events from a cytoplasmic open conformation to a periplasmic open conformation with the dynamic importance sampling molecular dynamics method and observed occluded intermediates. Analysis of water permeation pathways and the electrostatic free-energy landscape of a solvated proton indicated that the occluded state contains a solvated central cavity inaccessible from either side of the membrane. We propose a pair of geometric order parameters that capture the state of the pathway through the MFS transporters as shown by a survey of available crystal structures and models. We present a model for the occluded state of apo-LacY, which is similar to the occluded crystal structures of the MFS transporters EmrD, PepTSo, NarU, PiPT and XylE. Our simulations are consistent with experimental double electron spin–spin distance measurements that have been interpreted to show occluded conformations. During the simulations, a salt bridge that has been postulated to be involved in driving the conformational transition formed. Our results argue against a simple rigid-body domain motion as implied by a strict “rocker-switch mechanism” and instead hint at an intricate coupling between two flexible gates. The transport mechanism of LacY is hypothesized to involve an intermediate “occluded” state. Such a state is observed in computer simulations of the conformational transitions. Simulation data are validated with experimental double electron–electron spin resonance measurements. The structural gating elements of LacY are identified. Occluded LacY is similar to known occluded structures of homologous proteins.
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Affiliation(s)
- Lukas S. Stelzl
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Philip W. Fowler
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Mark S.P. Sansom
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Oliver Beckstein
- Center for Biological Physics, Department of Physics, Arizona State University, Tempe, AZ 85287, USA
- Corresponding author Department of Physics, Center for Biological Physics, Arizona State University, P.O. Box 871504, Tempe, AZ 85287-1504, USA.
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130
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Crystal structure of the plant dual-affinity nitrate transporter NRT1.1. Nature 2014; 507:73-7. [PMID: 24572362 PMCID: PMC3968801 DOI: 10.1038/nature13074] [Citation(s) in RCA: 195] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2013] [Accepted: 01/23/2014] [Indexed: 01/24/2023]
Abstract
Nitrate is a primary nutrient for plant growth, but its levels in soil can fluctuate by several orders of magnitude. Previous studies have identified Arabidopsis NRT1.1 as a dual-affinity nitrate transporter, which can take up nitrate over a wide range of concentrations. The mode of action of NRT1.1 is controlled by phosphorylation of a key residue, Thr101. Yet how this posttranslational modification switches the transporter between two affinity states remains unclear. Here we report the crystal structure of unphosphorylated NRT1.1, which reveals an unexpected homodimer in the inward-facing conformation. In this low-affinity state, the Thr101 phosphorylation site is embedded in a pocket immediately adjacent to the dimer interface, linking the phosphorylation status of the transporter to its oligomeric state. Using a cell-based fluorescence resonance energy transfer assay, we show that functional NRT1.1 indeed dimerizes in the cell membrane and the phosphomimetic mutation of Thr101 converts the protein into a monophasic high affinity transporter by structurally decoupling the dimer. Together with analyses of the substrate transport tunnel, our results establish a phosphorylation-controlled dimerization switch that allows NRT1.1 to uptake nitrate with two distinct affinity modes.
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131
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Harris NJ, Findlay HE, Simms J, Liu X, Booth PJ. Relative domain folding and stability of a membrane transport protein. J Mol Biol 2014; 426:1812-25. [PMID: 24530957 DOI: 10.1016/j.jmb.2014.01.012] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2013] [Revised: 01/30/2014] [Accepted: 01/31/2014] [Indexed: 10/25/2022]
Abstract
There is a limited understanding of the folding of multidomain membrane proteins. Lactose permease (LacY) of Escherichia coli is an archetypal member of the major facilitator superfamily of membrane transport proteins, which contain two domains of six transmembrane helices each. We exploit chemical denaturation to determine the unfolding free energy of LacY and employ Trp residues as site-specific thermodynamic probes. Single Trp LacY mutants are created with the individual Trps situated at mirror image positions on the two LacY domains. The changes in Trp fluorescence induced by urea denaturation are used to construct denaturation curves from which unfolding free energies can be determined. The majority of the single Trp tracers report the same stability and an unfolding free energy of approximately +2 kcal mol(-1). There is one exception; the fluorescence of W33 at the cytoplasmic end of helix I on the N domain is unaffected by urea. In contrast, the equivalent position on the first helix, VII, of the C-terminal domain exhibits wild-type stability, with the single Trp tracer at position 243 on helix VII reporting an unfolding free energy of +2 kcal mol(-1). This indicates that the region of the N domain of LacY at position 33 on helix I has enhanced stability to urea, when compared the corresponding location at the start of the C domain. We also find evidence for a potential network of stabilising interactions across the domain interface, which reduces accessibility to the hydrophilic substrate binding pocket between the two domains.
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Affiliation(s)
- Nicola J Harris
- School of Biochemistry, University of Bristol, Bristol BS8 1TD, UK
| | | | - John Simms
- School of Biochemistry, University of Bristol, Bristol BS8 1TD, UK
| | - Xia Liu
- School of Biochemistry, University of Bristol, Bristol BS8 1TD, UK
| | - Paula J Booth
- School of Biochemistry, University of Bristol, Bristol BS8 1TD, UK
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132
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Fonseca MV, Swanson MS. Nutrient salvaging and metabolism by the intracellular pathogen Legionella pneumophila. Front Cell Infect Microbiol 2014; 4:12. [PMID: 24575391 PMCID: PMC3920079 DOI: 10.3389/fcimb.2014.00012] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2013] [Accepted: 01/23/2014] [Indexed: 11/13/2022] Open
Abstract
The Gram-negative bacterium Legionella pneumophila is ubiquitous in freshwater environments as a free-swimming organism, resident of biofilms, or parasite of protozoa. If the bacterium is aerosolized and inhaled by a susceptible human host, it can infect alveolar macrophages and cause a severe pneumonia known as Legionnaires' disease. A sophisticated cell differentiation program equips L. pneumophila to persist in both extracellular and intracellular niches. During its life cycle, L. pneumophila alternates between at least two distinct forms: a transmissive form equipped to infect host cells and evade lysosomal degradation, and a replicative form that multiplies within a phagosomal compartment that it has retooled to its advantage. The efficient changeover between transmissive and replicative states is fundamental to L. pneumophila's fitness as an intracellular pathogen. The transmission and replication programs of L. pneumophila are governed by a number of metabolic cues that signal whether conditions are favorable for replication or instead trigger escape from a spent host. Several lines of experimental evidence gathered over the past decade establish strong links between metabolism, cellular differentiation, and virulence of L. pneumophila. Herein, we focus on current knowledge of the metabolic components employed by intracellular L. pneumophila for cell differentiation, nutrient salvaging and utilization of host factors. Specifically, we highlight the metabolic cues that are coupled to bacterial differentiation, nutrient acquisition systems, and the strategies utilized by L. pneumophila to exploit host metabolites for intracellular replication.
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Affiliation(s)
- Maris V Fonseca
- Science and Mathematics Division, Monroe County Community College Monroe, MI, USA
| | - Michele S Swanson
- Department of Microbiology and Immunology, University of Michigan Medical School Ann Arbor, MI, USA
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133
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Valdés R, Elferich J, Shinde U, Landfear SM. Identification of the intracellular gate for a member of the equilibrative nucleoside transporter (ENT) family. J Biol Chem 2014; 289:8799-809. [PMID: 24497645 DOI: 10.1074/jbc.m113.546960] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Equilibrative nucleoside transporters of the SLC29 family play important roles in many physiological and pharmacological processes, including import of drugs for treatment of cancer, AIDS, cardiovascular, and parasitic diseases. However, no crystal structure is available for any member of this family. In previous studies we generated a computational model of the Leishmania donovani nucleoside transporter 1.1 (LdNT1.1) that captured this permease in the outward-closed conformation, and we identified the extracellular gate. In the present study we have modeled the inward-closed conformation of LdNT1.1 using the crystal structure of the Escherichia coli fucose transporter FucP and have identified four transmembrane helices whose ends close to form a predicted intracellular gate. We have tested this prediction by site-directed mutagenesis of relevant helix residues and by cross-linking of introduced cysteine pairs. The results are consistent with the predictions of the computational model and suggest that a similarly constituted gate operates in other members of the equilibrative nucleoside transporter family.
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Affiliation(s)
- Raquel Valdés
- From the Departments of Molecular Microbiology and Immunology and
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134
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Abstract
The Major Facilitator Superfamily (MFS) is a diverse group of secondary transporters with over 10,000 members, found in all kingdoms of life, including Homo sapiens. One objective of determining crystallographic models of the bacterial representatives is identification and physical localization of residues important for catalysis in transporters with medical relevance. The recently solved crystallographic models of the D-xylose permease XylE from Escherichia coli and GlcP from Staphylococcus epidermidus, homologs of the human D-glucose transporters, the GLUTs (SLC2), provide information about the structure of these transporters. The goal of this work is to examine general concepts derived from the bacterial XylE, GlcP, and other MFS transporters for their relevance to the GLUTs by comparing conservation of functionally critical residues. An energy landscape for symport and uniport is presented. Furthermore, the substrate selectivity of XylE is compared with GLUT1 and GLUT5, as well as a XylE mutant that transports D-glucose.
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135
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Masureel M, Martens C, Stein RA, Mishra S, Ruysschaert JM, Mchaourab HS, Govaerts C. Protonation drives the conformational switch in the multidrug transporter LmrP. Nat Chem Biol 2014; 10:149-55. [PMID: 24316739 PMCID: PMC4749020 DOI: 10.1038/nchembio.1408] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2013] [Accepted: 10/18/2013] [Indexed: 02/07/2023]
Abstract
Multidrug antiporters of the major facilitator superfamily couple proton translocation to the extrusion of cytotoxic molecules. The conformational changes that underlie the transport cycle and the structural basis of coupling of these transporters have not been elucidated. Here we used extensive double electron-electron resonance measurements to uncover the conformational equilibrium of LmrP, a multidrug transporter from Lactococcus lactis, and to investigate how protons and ligands shift this equilibrium to enable transport. We find that the transporter switches between outward-open and outward-closed conformations, depending on the protonation states of specific acidic residues forming a transmembrane protonation relay. Our data can be framed in a model of transport wherein substrate binding initiates the transport cycle by opening the extracellular side. Subsequent protonation of membrane-embedded acidic residues induces substrate release to the extracellular side and triggers a cascade of conformational changes that concludes in proton release to the intracellular side.
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Affiliation(s)
- Matthieu Masureel
- 1] Laboratory for the Structure and Function of Biological Membranes, Center for Structural Biology and Bioinformatics, Université Libre de Bruxelles, Brussels, Belgium. [2]
| | - Chloé Martens
- 1] Laboratory for the Structure and Function of Biological Membranes, Center for Structural Biology and Bioinformatics, Université Libre de Bruxelles, Brussels, Belgium. [2]
| | - Richard A Stein
- Department of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Smriti Mishra
- Department of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Jean-Marie Ruysschaert
- Laboratory for the Structure and Function of Biological Membranes, Center for Structural Biology and Bioinformatics, Université Libre de Bruxelles, Brussels, Belgium
| | - Hassane S Mchaourab
- 1] Department of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, Tennessee, USA. [2]
| | - Cédric Govaerts
- 1] Laboratory for the Structure and Function of Biological Membranes, Center for Structural Biology and Bioinformatics, Université Libre de Bruxelles, Brussels, Belgium. [2]
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136
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Perlin MH, Andrews J, San Toh S. Essential Letters in the Fungal Alphabet. ADVANCES IN GENETICS 2014; 85:201-53. [DOI: 10.1016/b978-0-12-800271-1.00004-4] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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137
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The Life and Times of Lac Permease: Crystals Ain’t Everything, but They Certainly Do Help. SPRINGER SERIES IN BIOPHYSICS 2014. [DOI: 10.1007/978-3-642-53839-1_6] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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138
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Boudker O, Akyuz N. Dance Lessons for Proteins: The Dynamics and Thermodynamics of a Sodium/Aspartate Symporter. SPRINGER SERIES IN BIOPHYSICS 2014. [DOI: 10.1007/978-3-642-53839-1_1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/08/2022]
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139
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Ethayathulla AS, Yousef MS, Amin A, Leblanc G, Kaback HR, Guan L. Structure-based mechanism for Na(+)/melibiose symport by MelB. Nat Commun 2014; 5:3009. [PMID: 24389923 PMCID: PMC4026327 DOI: 10.1038/ncomms4009] [Citation(s) in RCA: 114] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2013] [Accepted: 11/22/2013] [Indexed: 12/12/2022] Open
Abstract
The bacterial melibiose permease (MelB) belongs to the glycoside-pentoside-hexuronide:cation symporter family, a part of the major facilitator superfamily (MFS). Structural information regarding glycoside-pentoside-hexuronide:cation symporter family transporters and other Na(+)-coupled permeases within MFS has been lacking, although a wealth of biochemical and biophysical data are available. Here we present the three-dimensional crystal structures of Salmonella typhimurium MelBSt in two conformations, representing an outward partially occluded and an outward inactive state of MelBSt. MelB adopts a typical MFS fold and contains a previously unidentified cation-binding motif. Three conserved acidic residues form a pyramidal-shaped cation-binding site for Na(+), Li(+) or H(+), which is in close proximity to the sugar-binding site. Both cosubstrate-binding sites are mainly contributed by the residues from the amino-terminal domain. These two structures and the functional data presented here provide mechanistic insights into Na(+)/melibiose symport. We also postulate a structural foundation for the conformational cycling necessary for transport catalysed by MFS permeases in general.
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Affiliation(s)
- Abdul S. Ethayathulla
- Department of Cell Physiology and Molecular Biophysics, Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, Texas 79430, USA
| | - Mohammad S. Yousef
- Department of Cell Physiology and Molecular Biophysics, Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, Texas 79430, USA
- Present address: Department of Physics, College of Arts and Sciences, Southern Illinois University, Edwardsville, Illinois 62026-1654, USA (on leave from: Biophysics Department, Faculty of Science, Cairo University, Egypt)
| | - Anowarul Amin
- Department of Cell Physiology and Molecular Biophysics, Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, Texas 79430, USA
| | - Gérard Leblanc
- Department of Physiology, University of California, Los Angeles, California 90095, USA
- Present address: CEA-DSV-Fontenay aux Roses, Cross Division of Toxicology, 92 265 Fontenay aux Roses BP 6, France
| | - H. Ronald Kaback
- Department of Physiology, University of California, Los Angeles, California 90095, USA
| | - Lan Guan
- Department of Cell Physiology and Molecular Biophysics, Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, Texas 79430, USA
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140
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Wong K, Ma J, Rothnie A, Biggin PC, Kerr ID. Towards understanding promiscuity in multidrug efflux pumps. Trends Biochem Sci 2013; 39:8-16. [PMID: 24316304 DOI: 10.1016/j.tibs.2013.11.002] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2013] [Revised: 10/31/2013] [Accepted: 11/05/2013] [Indexed: 10/25/2022]
Abstract
Drug export from cells is a major factor in the acquisition of cellular resistance to antimicrobial and cancer chemotherapy, and poses a significant threat to future clinical management of disease. Many of the proteins that catalyse drug efflux do so with remarkably low substrate specificity, a phenomenon known as multidrug transport. For these reasons we need a greater understanding of drug recognition and transport in multidrug pumps to inform research that attempts to circumvent their action. Structural and computational studies have been heralded as being great strides towards a full elucidation of multidrug recognition and transport. In this review we summarise these advances and ask how close we are to a molecular understanding of this remarkable phenomenon.
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Affiliation(s)
- Kelvin Wong
- School of Life Sciences, Queen's Medical Centre, University of Nottingham, Nottingham, NG7 2UH, UK
| | - Jerome Ma
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, UK
| | - Alice Rothnie
- Life & Health Sciences, Aston University, Aston Triangle, Birmingham, B4 7ET, UK
| | - Philip C Biggin
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, UK
| | - Ian D Kerr
- School of Life Sciences, Queen's Medical Centre, University of Nottingham, Nottingham, NG7 2UH, UK.
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141
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Abstract
One fundamentally important problem for understanding the mechanism of coupling between substrate and H(+) translocation with secondary active transport proteins is the identification and physical localization of residues involved in substrate and H(+) binding. This information is exceptionally difficult to obtain with the Major Facilitator Superfamily (MFS) because of the broad sequence diversity of the members. The MFS is the largest and most diverse group of transporters, many of which are clinically important, and includes members from all kingdoms of life. A wide range of substrates is transported, in many instances against a concentration gradient by transduction of the energy stored in an H(+) electrochemical gradient using symport mechanisms, which are discussed herein. Crystallographic structures of MFS members indicate that a deep central hydrophilic cavity surrounded by 12 mostly irregular transmembrane helices represents a common structural feature. An inverted triple-helix structural symmetry motif within the N- and C-terminal six-helix bundles suggests that the proteins may have arisen by intragenic multiplication. In the work presented here, the triple-helix motifs are aligned in combinatorial fashion so as to detect functionally homologous positions with known atomic structures of MFS members. Substrate and H(+)-binding sites in symporters that transport substrates, ranging from simple ions like phosphate to more complex peptides or disaccharides, are found to be in similar locations. It also appears likely that there is a homologous ordered kinetic mechanism for the H(+)-coupled MFS symporters.
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142
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Cura AJ, Carruthers A. Role of monosaccharide transport proteins in carbohydrate assimilation, distribution, metabolism, and homeostasis. Compr Physiol 2013; 2:863-914. [PMID: 22943001 DOI: 10.1002/cphy.c110024] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The facilitated diffusion of glucose, galactose, fructose, urate, myoinositol, and dehydroascorbicacid in mammals is catalyzed by a family of 14 monosaccharide transport proteins called GLUTs. These transporters may be divided into three classes according to sequence similarity and function/substrate specificity. GLUT1 appears to be highly expressed in glycolytically active cells and has been coopted in vitamin C auxotrophs to maintain the redox state of the blood through transport of dehydroascorbate. Several GLUTs are definitive glucose/galactose transporters, GLUT2 and GLUT5 are physiologically important fructose transporters, GLUT9 appears to be a urate transporter while GLUT13 is a proton/myoinositol cotransporter. The physiologic substrates of some GLUTs remain to be established. The GLUTs are expressed in a tissue specific manner where affinity, specificity, and capacity for substrate transport are paramount for tissue function. Although great strides have been made in characterizing GLUT-catalyzed monosaccharide transport and mapping GLUT membrane topography and determinants of substrate specificity, a unifying model for GLUT structure and function remains elusive. The GLUTs play a major role in carbohydrate homeostasis and the redistribution of sugar-derived carbons among the various organ systems. This is accomplished through a multiplicity of GLUT-dependent glucose sensing and effector mechanisms that regulate monosaccharide ingestion, absorption,distribution, cellular transport and metabolism, and recovery/retention. Glucose transport and metabolism have coevolved in mammals to support cerebral glucose utilization.
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Affiliation(s)
- Anthony J Cura
- Department of Biochemistry & Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts, USA
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143
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Steed PR, Zou P, Trone KE, Mchaourab HS. Structure and pH-induced structural rearrangements of the putative multidrug efflux pump EmrD in liposomes probed by site-directed spin labeling. Biochemistry 2013; 52:7964-74. [PMID: 24148002 DOI: 10.1021/bi4012385] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
EmrD is the only structurally characterized drug/H(+) antiporter of the major facilitator superfamily (MFS). It has been crystallized in a doubly occluded conformation that is considered representative of an intermediate state in the transport cycle of MFS transporters. However, unexpected features of the crystal structure and the lack of functional information available for EmrD limit the utility of the structural data. To assess whether the crystal structure represents a stable state in a native-like environment, we used electron paramagnetic resonance (EPR) spectroscopy to determine the mobility and accessibility of spin labels at 76 positions in six transmembrane (TM) helices of EmrD reconstituted in liposomes. While the EPR data were mostly consistent with the crystal structure, they also revealed significant deviations from the predicted orientation and topology of TM helices at several locations. Additionally, we were unable to reproduce EmrD-dependent multidrug resistance phenotypes in vitro and in cell-based assays of drug transport. In spite of structural and functional discrepancies, we mapped a pH-dependent conformational change in which the cytoplasmic side of the N-terminal half opened locally in response to protonation. This conformational switch is consistent with the expected pH-dependent behavior of MFS H(+)-coupled antiporters.
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Affiliation(s)
- P Ryan Steed
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232
| | - Ping Zou
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232
| | - Kristin E Trone
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232
| | - Hassane S Mchaourab
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232
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144
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145
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Duddempudi PK, Goyal R, Date SS, Jansen M. Delineating the extracellular water-accessible surface of the proton-coupled folate transporter. PLoS One 2013; 8:e78301. [PMID: 24205192 PMCID: PMC3799626 DOI: 10.1371/journal.pone.0078301] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2013] [Accepted: 09/16/2013] [Indexed: 11/19/2022] Open
Abstract
The proton-coupled folate transporter (PCFT) was recently identified as the major uptake route for dietary folates in humans. The three-dimensional structure of PCFT and its detailed interplay with function remain to be determined. We screened the water-accessible extracellular surface of HsPCFT using the substituted-cysteine accessibility method, to investigate the boundaries between the water-accessible surface and inaccessible buried protein segments. Single-cysteines, engineered individually at 40 positions in a functional cysteine-less HsPCFT background construct, were probed for plasma-membrane expression in Xenopus oocytes with a bilayer-impermeant primary-amine-reactive biotinylating agent (sulfosuccinimidyl 6-(biotinamido) hexanoate), and additionally for water-accessibility of the respective engineered cysteine with the sulfhydryl-selective biotinylating agent 2-((biotinoyl)amino)ethyl methanethiosulfonate. The ratio between Cys-selective over amine-selective labeling was further used to evaluate three-dimensional models of HsPCFT generated by homology / threading modeling. The closest homologues of HsPCFT with a known experimentally-determined three-dimensional structure are all members of one of the largest membrane protein super-families, the major facilitator superfamily (MFS). The low sequence identity - 14% or less – between HsPCFT and these templates necessitates experiment-based evaluation and model refinement of homology / threading models. With the present set of single-cysteine accessibilities, the models based on GlpT and PepTSt are most promising for further refinement.
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Affiliation(s)
- Phaneendra Kumar Duddempudi
- Department of Pharmacology and Neuroscience, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, Texas, United States of America
- Center for Membrane Protein Research, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, Texas, United States of America
| | - Raman Goyal
- Center for Membrane Protein Research, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, Texas, United States of America
- Department of Cell Physiology and Molecular Biophysics, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, Texas, United States of America
| | - Swapneeta Sanjay Date
- Center for Membrane Protein Research, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, Texas, United States of America
- Department of Cell Physiology and Molecular Biophysics, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, Texas, United States of America
| | - Michaela Jansen
- Center for Membrane Protein Research, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, Texas, United States of America
- Department of Cell Physiology and Molecular Biophysics, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, Texas, United States of America
- * E-mail:
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146
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Abstract
Glucose transporters are required to bring glucose into cells, where it is an essential energy source and precursor in protein and lipid synthesis. These transporters are involved in important common diseases such as cancer and diabetes. Here, we report the crystal structure of the Staphylococcus epidermidis glucose/H(+) symporter in an inward-facing conformation at 3.2-Å resolution. The Staphylococcus epidermidis glucose/H(+) symporter is homologous to human glucose transporters, is very specific and has high avidity for glucose, and is inhibited by the human glucose transport inhibitors cytochalasin B, phloretin, and forskolin. On the basis of the crystal structure in conjunction with mutagenesis and functional studies, we propose a mechanism for glucose/H(+) symport and discuss the symport mechanism versus facilitated diffusion.
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147
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Peptide transporter DtpA has two alternate conformations, one of which is promoted by inhibitor binding. Proc Natl Acad Sci U S A 2013; 110:E3978-86. [PMID: 24082128 DOI: 10.1073/pnas.1312959110] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Peptide transporters (PTRs) of the large PTR family facilitate the uptake of di- and tripeptides to provide cells with amino acids for protein synthesis and for metabolic intermediates. Although several PTRs have been structurally and functionally characterized, how drugs modulate peptide transport remains unclear. To obtain insight into this mechanism, we characterize inhibitor binding to the Escherichia coli PTR dipeptide and tripeptide permease A (DtpA), which shows substrate specificities similar to its human homolog hPEPT1. After demonstrating that Lys[Z-NO2]-Val, the strongest inhibitor of hPEPT1, also acts as a high-affinity inhibitor for DtpA, we used single-molecule force spectroscopy to localize the structural segments stabilizing the peptide transporter and investigated which of these structural segments change stability upon inhibitor binding. This characterization was done with DtpA embedded in the lipid membrane and exposed to physiologically relevant conditions. In the unbound state, DtpA adopts two main alternate conformations in which transmembrane α-helix (TMH) 2 is either stabilized (in ∼43% of DtpA molecules) or not (in ∼57% of DtpA molecules). The two conformations are understood to represent the inward- and outward-facing conformational states of the transporter. With increasing inhibitor concentration, the conformation characterized by a stabilized TMH 2 becomes increasingly prevalent, reaching ∼92% at saturation. Our measurements further suggest that Lys[Z-NO2]-Val interacts with discrete residues in TMH 2 that are important for ligand binding and substrate affinity. These interactions in turn stabilize TMH 2, thereby promoting the inhibited conformation of DtpA.
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148
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Song J, Ji C, Zhang JZH. Insights on Na(+) binding and conformational dynamics in multidrug and toxic compound extrusion transporter NorM. Proteins 2013; 82:240-9. [PMID: 23873591 DOI: 10.1002/prot.24368] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2013] [Revised: 06/19/2013] [Accepted: 07/09/2013] [Indexed: 12/23/2022]
Abstract
MATE (multidrug and toxic compound extrusion) transporter proteins mediate metabolite transport in plants and multidrug resistance in bacteria and mammals. MATE transporter NorM from Vibrio cholerae is an antiporter that is driven by Na+ gradient to extrude the substrates. To understand the molecular mechanism of Na+-substrate exchange, molecular dynamics simulation was performed to study conformational changes of both wild-type and mutant NorM with and without cation bindings. Our results show that NorM is able to bind two Na(+) ions simultaneously, one to each of the carboxylic groups of E255 and D371 in the binding pocket. Furthermore, this di-Na(+) binding state is likely more efficient for conformational changes of NorM_VC toward the inward-facing conformation than single-Na(+) binding state. The observation of two Na(+) binding sites of NorM_VC is consistent with the previous study that two sites for ion binding (denoted as Na1/Na2 sites) are found in the transporter LeuT and BetP, another two secondary transporters. Taken together, our findings shed light on the structure rearrangements of NorM on Na(+) binding and enrich our knowledge of the transport mechanism of secondary transporters.
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Affiliation(s)
- Jianing Song
- State Key Laboratory of Precision Spectroscopy, Department of Physics, Institute of Theoretical and Computational Science, East China Normal University, Shanghai, 200062, China
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149
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Le Gac G, Ka C, Joubrel R, Gourlaouen I, Lehn P, Mornon JP, Férec C, Callebaut I. Structure-function analysis of the human ferroportin iron exporter (SLC40A1): effect of hemochromatosis type 4 disease mutations and identification of critical residues. Hum Mutat 2013; 34:1371-80. [PMID: 23784628 DOI: 10.1002/humu.22369] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2013] [Accepted: 06/06/2013] [Indexed: 11/06/2022]
Abstract
Ferroportin (SLC40A1) is the only known iron exporter in mammals and is considered a key coordinator of the iron balance between intracellular and systemic iron homeostasis. However, the structural organization of ferroportin in the lipid bilayer remains controversial and very little is known about the mechanism underlying iron egress. In the present study, we have developed an approach based on comparative modeling, which has led to the construction of a model of the three-dimensional (3D) structure of ferroportin by homology to the crystal structure of a Major Facilitator Superfamily member (EmrD). This model predicts atomic details for the organization of ferroportin transmembrane helices and is in agreement with our current understanding of the ferroportin function and its interaction with hepcidin. Using in vitro experiments, we demonstrate that this model can be used to identify novel critical amino acids. In particular, we show that the tryptophan residue 42 (p.Trp42), which is localized within the extracellular end of the ferroportin pore, is likely involved in both the iron export function and in the mechanism of inhibition by hepcidin. Thus, our 3D model provides a new perspective for understanding the molecular basis of ferroportin functions and dysfunctions.
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Affiliation(s)
- Gérald Le Gac
- Inserm UMR1078, Université de Brest, SFR SnInBioS, Centre Hospitalier Régional Universitaire - Laboratoire de Génétique Moléculaire et d'Histocompatibilité, Etablissement Français du Sang - Bretagne, Brest, France
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Mueckler M, Thorens B. The SLC2 (GLUT) family of membrane transporters. Mol Aspects Med 2013. [PMID: 23506862 DOI: 10.1016/j.mam.2012.07.001,] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/30/2022]
Abstract
GLUT proteins are encoded by the SLC2 genes and are members of the major facilitator superfamily of membrane transporters. Fourteen GLUT proteins are expressed in the human and they are categorized into three classes based on sequence similarity. All GLUTs appear to transport hexoses or polyols when expressed ectopically, but the primary physiological substrates for several of the GLUTs remain uncertain. GLUTs 1-5 are the most thoroughly studied and all have well established roles as glucose and/or fructose transporters in various tissues and cell types. The GLUT proteins are comprised of ∼500 amino acid residues, possess a single N-linked oligosaccharide, and have 12 membrane-spanning domains. In this review we briefly describe the major characteristics of the 14 GLUT family members.
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Affiliation(s)
- Mike Mueckler
- Department of Cell Biology, Washington University School of Medicine, St. Louis, MO 63110, USA.
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