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X-ray structure of LeuT in an inward-facing occluded conformation reveals mechanism of substrate release

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  • Kamil Gotfryd, Molecular Neuropharmacology and Genetics Laboratory, Kobenhavns Universitet, Department of Biomedical Sciences
  • ,
  • Thomas Boesen
  • Jonas S. Mortensen, Kobenhavns Universitet
  • ,
  • George Khelashvili, Cornell University
  • ,
  • Matthias Quick, Columbia University
  • ,
  • Daniel S. Terry, St. Jude Children Research Hospital
  • ,
  • Julie W. Missel, Kobenhavns Universitet
  • ,
  • Michael V. LeVine, Cornell University
  • ,
  • Pontus Gourdon, Department of Biomedical Sciences, Kobenhavns Universitet
  • ,
  • Scott C. Blanchard, St. Jude Children Research Hospital
  • ,
  • Jonathan A. Javitch, Columbia University
  • ,
  • Harel Weinstein, Cornell University
  • ,
  • Claus J. Loland, Molecular Neuropharmacology and Genetics Laboratory, Kobenhavns Universitet
  • ,
  • Poul Nissen
  • Ulrik Gether, Molecular Neuropharmacology and Genetics Laboratory, Kobenhavns Universitet

Neurotransmitter:sodium symporters (NSS) are conserved from bacteria to man and serve as targets for drugs, including antidepressants and psychostimulants. Here we report the X-ray structure of the prokaryotic NSS member, LeuT, in a Na+/substrate-bound, inward-facing occluded conformation. To obtain this structure, we were guided by findings from single-molecule fluorescence spectroscopy and molecular dynamics simulations indicating that L-Phe binding and mutation of the conserved N-terminal Trp8 to Ala both promote an inward-facing state. Compared to the outward-facing occluded conformation, our structure reveals a major tilting of the cytoplasmic end of transmembrane segment (TM) 5, which, together with release of the N-terminus but without coupled movement of TM1, opens a wide cavity towards the second Na+ binding site. The structure of this key intermediate in the LeuT transport cycle, in the context of other NSS structures, leads to the proposal of an intracellular release mechanism of substrate and ions in NSS proteins.

Original languageEnglish
Article number1005
JournalNature Communications
Number of pages14
Publication statusPublished - 21 Feb 2020

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