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Shaheen A, Tariq A, Ismat F, Naveed H, De Zorzi R, Iqbal M, Storici P, Mirza O, Walz T, Rahman M. Identification of additional mechanistically important residues in the multidrug transporter styMdtM of Salmonella Typhi. J Biomol Struct Dyn 2023:1-10. [PMID: 37787617 DOI: 10.1080/07391102.2023.2263882] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2023] [Accepted: 09/19/2023] [Indexed: 10/04/2023]
Abstract
Multidrug efflux is a well-established mechanism of drug resistance in bacterial pathogens like Salmonella Typhi. styMdtM (locus name; STY4874) is a multidrug efflux transporter of the major facilitator superfamily expressed in S. Typhi. Functional assays identified several residues important for its transport activity. Here, we used an AlphaFold model to identify additional residues for analysis by mutagenesis. Mutation of peripheral residue Cys185 had no effect on the structure or function of the transporter. However, substitution of channel-lining residues Tyr29 and Tyr231 completely abolished transport function. Finally, mutation of Gln294, which faces peripheral helices of the transporter, resulted in the loss of transport of some substrates. Crystallization studies yielded diffraction data for the wild-type protein at 4.5 Å resolution and allowed the unit cell parameters to be established as a = b = 64.3 Å, c = 245.4 Å, α = β = γ = 90°, in space group P4. Our studies represent a further stepping stone towards a mechanistic understanding of the clinically important multidrug transporter styMdtM.Communicated by Ramaswamy H. Sarma.
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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
- Department of Biochemistry and Biotechnology, University of Gujrat, Gujrat, Pakistan
- Department of Cell Biology, Harvard Medical School, Boston, MA, USA
| | - Anam Tariq
- Drug Discovery and Structural Biology Group, Health Biotechnology Division, National Institute for Biotechnology and Genetic Engineering (NIBGE), Faisalabad, Pakistan
- Protein Facility, Elettra Sincrotrone Trieste S.C.p.A, Trieste, Italy
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MA, USA
| | - Fouzia Ismat
- Drug Discovery and Structural Biology Group, Health Biotechnology Division, National Institute for Biotechnology and Genetic Engineering (NIBGE), Faisalabad, Pakistan
| | - Hammad Naveed
- Department of Computer Science, National University of Computer & Emerging Sciences - FAST, Lahore, Pakistan
| | - Rita De Zorzi
- Department of Cell Biology, Harvard Medical School, Boston, MA, USA
- Department of Chemical and Pharmaceutical Sciences, University of Trieste, Trieste, Italy
| | - Mazhar Iqbal
- Drug Discovery and Structural Biology Group, Health Biotechnology Division, National Institute for Biotechnology and Genetic Engineering (NIBGE), Faisalabad, Pakistan
| | - Paola Storici
- Protein Facility, Elettra Sincrotrone Trieste S.C.p.A, Trieste, Italy
| | - 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, USA
- Laboratory of Molecular Electron Microscopy, Rockefeller University, New York, NY, USA
| | - Moazur Rahman
- Drug Discovery and Structural Biology Group, Health Biotechnology Division, National Institute for Biotechnology and Genetic Engineering (NIBGE), Faisalabad, Pakistan
- Department of Cell Biology, Harvard Medical School, Boston, MA, USA
- School of Biological Sciences, University of the Punjab, Lahore, Pakistan
- Center of Excellence in Molecular Biology, University of the Punjab, Lahore, Pakistan
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Competition between protons and substrate for binding to the major facilitator superfamily multidrug/H + antiporter MdtM. EXPERIMENTAL RESULTS 2021. [DOI: 10.1017/exp.2021.26] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Abstract
Proton electrochemical gradient-driven multidrug efflux activity of representatives of the major facilitator superfamily (MFS) of secondary active transporters contributes to antimicrobial resistance of pathogenic bacteria. Integral to the mechanism of these transporters is a proposed competition between substrate and protons for the binding site of the protein. The current work investigated the competition between protons and antimicrobial substrate for binding to the Escherichia coli MFS multidrug/H+ antiporter MdtM by measuring the quench of intrinsic protein fluorescence upon titration of substrate tetraphenylphosphonium into a solution of purified MdtM over a range of pH values between pH 8.8 and 5.9. The results, which revealed that protons inhibit binding of substrate to MdtM in a competitive manner, are consistent with those reported in a study on the related MFS multidrug/H+ antiporter MdfA and provide further evidence that competition for binding between substrate and protons is a general feature of secondary multidrug efflux.
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Clamping down on drugs: the Escherichia coli multidrug efflux protein MdtM. Res Microbiol 2017; 169:461-467. [PMID: 28962921 DOI: 10.1016/j.resmic.2017.09.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2017] [Revised: 09/19/2017] [Accepted: 09/21/2017] [Indexed: 11/22/2022]
Abstract
Multidrug resistance is principally a consequence of the active transport of drugs out of the cell by proteins that are integral membrane transporters. In the following review, we present a synthesis of current understanding of the Escherichia coli multidrug resistance transporter, MdtM, a 410 amino acid residue protein that belongs to the large and ubiquitous major facilitator superfamily (MFS).
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Labarbuta P, Duckett K, Botting CH, Chahrour O, Malone J, Dalton JP, Law CJ. Recombinant vacuolar iron transporter family homologue PfVIT from human malaria-causing Plasmodium falciparum is a Fe 2+/H +exchanger. Sci Rep 2017; 7:42850. [PMID: 28198449 PMCID: PMC5309874 DOI: 10.1038/srep42850] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2016] [Accepted: 01/18/2017] [Indexed: 02/08/2023] Open
Abstract
Vacuolar iron transporters (VITs) are a poorly understood family of integral membrane proteins that can function in iron homeostasis via sequestration of labile Fe2+ into vacuolar compartments. Here we report on the heterologous overexpression and purification of PfVIT, a vacuolar iron transporter homologue from the human malaria-causing parasite Plasmodium falciparum. Use of synthetic, codon-optimised DNA enabled overexpression of functional PfVIT in the inner membrane of Escherichia coli which, in turn, conferred iron tolerance to the bacterial cells. Cells that expressed PfVIT had decreased levels of total cellular iron compared with cells that did not express the protein. Qualitative transport assays performed on inverted vesicles enriched with PfVIT revealed that the transporter catalysed Fe2+/H+ exchange driven by the proton electrochemical gradient. Furthermore, the PfVIT transport function in this system did not require the presence of any Plasmodium-specific factor such as post-translational phosphorylation. PfVIT purified as a monomer and, as measured by intrinsic protein fluorescence quenching, bound Fe2+ in detergent solution with low micromolar affinity. This study of PfVIT provides material for future detailed biochemical, biophysical and structural studies to advance understanding of the vacuolar iron transporter family of membrane proteins from important human pathogens.
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Affiliation(s)
- Paola Labarbuta
- School of Biological Sciences, Medical Biology Centre, Queen's University Belfast, Belfast BT9 7BL, United Kingdom
| | - Katie Duckett
- School of Biological Sciences, Medical Biology Centre, Queen's University Belfast, Belfast BT9 7BL, United Kingdom
| | - Catherine H Botting
- School of Biology, Biomedical Sciences Research Complex, University of St Andrews, North Haugh, St Andrews, Fife KY16 9ST, United Kingdom
| | - Osama Chahrour
- Spectroscopy Group, Analytical Services, Almac, 20 Seagoe Industrial Estate, Craigavon BT63 5QD, United Kingdom
| | - John Malone
- Spectroscopy Group, Analytical Services, Almac, 20 Seagoe Industrial Estate, Craigavon BT63 5QD, United Kingdom
| | - John P Dalton
- School of Biological Sciences, Medical Biology Centre, Queen's University Belfast, Belfast BT9 7BL, United Kingdom
| | - Christopher J Law
- School of Biological Sciences, Medical Biology Centre, Queen's University Belfast, Belfast BT9 7BL, United Kingdom
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Insight into determinants of substrate binding and transport in a multidrug efflux protein. Sci Rep 2016; 6:22833. [PMID: 26961153 PMCID: PMC4785361 DOI: 10.1038/srep22833] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2015] [Accepted: 02/24/2016] [Indexed: 11/09/2022] Open
Abstract
Multidrug resistance arising from the activity of integral membrane transporter proteins presents a global public health threat. In bacteria such as Escherichia coli, transporter proteins belonging to the major facilitator superfamily make a considerable contribution to multidrug resistance by catalysing efflux of myriad structurally and chemically different antimicrobial compounds. Despite their clinical relevance, questions pertaining to mechanistic details of how these promiscuous proteins function remain outstanding, and the role(s) played by individual amino acid residues in recognition, binding and subsequent transport of different antimicrobial substrates by multidrug efflux members of the major facilitator superfamily requires illumination. Using in silico homology modelling, molecular docking and mutagenesis studies in combination with substrate binding and transport assays, we identified several amino acid residues that play important roles in antimicrobial substrate recognition, binding and transport by Escherichia coli MdtM, a representative multidrug efflux protein of the major facilitator superfamily. Furthermore, our studies suggested that ‘aromatic clamps’ formed by tyrosine and phenylalanine residues located within the substrate binding pocket of MdtM may be important for antimicrobial substrate recognition and transport by the protein. Such ‘clamps’ may be a structurally and functionally important feature of all major facilitator multidrug efflux proteins.
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