title: Gating topology of the proton-coupled oligopeptide symporters.
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.
authors: Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK. Electronic address: philip.fowler@bioch.ox.ac.uk.
authors: Philip W
authors: PW
authors: Fowler
authors: Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK.
authors: Marcella
authors: M
authors: Orwick-Rydmark
authors: Max Planck Institute of Biophysics, Max-von-Laue-Straße 3, Frankfurt am Main, Germany.
authors: Sebastian
authors: S
authors: Radestock
authors: Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK.
authors: Nicolae
authors: N
authors: Solcan
authors: Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK.
authors: Patricia M
authors: PM
authors: Dijkman
authors: School of Biochemistry and Immunology, Trinity College Dublin, Dublin 2, Ireland.
authors: Joseph A
authors: JA
authors: Lyons
authors: Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK.
authors: Jane
authors: J
authors: Kwok
authors: School of Biochemistry and Immunology, Trinity College Dublin, Dublin 2, Ireland.
authors: Martin
authors: M
authors: Caffrey
authors: Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK.
authors: Anthony
authors: A
authors: Watts
authors: Max Planck Institute of Biophysics, Max-von-Laue-Straße 3, Frankfurt am Main, Germany.
authors: Lucy R
authors: LR
authors: Forrest
authors: Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK. Electronic address: simon.newstead@bioch.ox.ac.uk.
authors: Simon
authors: S
authors: Newstead
mesh_terms: D001419:Bacteria / Q000235:genetics* / Q000378:metabolism; D001693:Biological Transport, Active / Q000502:physiology; D003461:Crystallography; D004578:Electron Spin Resonance Spectroscopy; D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D011487:Protein Conformation; D013057:Spectrum Analysis; D027981:Symporters / Q000737:chemistry* / Q000378:metabolism
chemical_list: D027981:Symporters
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