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Gating topology of the proton-coupled oligopeptide symporters

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  • Philip W. Fowler, University of Oxford
  • ,
  • Marcella Orwick-Rydmark, University of Oxford
  • ,
  • Sebastian Radestock, Max Planck Institute of Biophysics
  • ,
  • Nicolae Solcan, University of Oxford
  • ,
  • Patricia M. Dijkman, University of Oxford
  • ,
  • Joseph A. Lyons
  • Jane Kwok, University of Oxford
  • ,
  • Martin Caffrey, Trinity College Dublin
  • ,
  • Anthony Watts, University of Oxford
  • ,
  • Lucy R. Forrest, Max Planck Institute of Biophysics
  • ,
  • Simon Newstead, University of Oxford

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.

Original languageEnglish
Pages (from-to)290-301
Number of pages12
Publication statusPublished - 3 Feb 2015
Externally publishedYes

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