X-ray Structure of LeuT in an Inward-facing Occluded Conformation Reveals Mechanism of Substrate Release

Overview

Journal Nat Commun

Specialty Biology

Date 2020 Feb 22

PMID 32081981

Citations 27

Authors

Kamil Gotfryd

Thomas Boesen

Jonas S Mortensen

George Khelashvili

Matthias Quick

Daniel S Terry

Julie W Missel

Michael V Levine

Pontus Gourdon

Scott C Blanchard

Jonathan A Javitch

Harel Weinstein

Claus J Loland

Poul Nissen

Ulrik Gether

Affiliations

Soon will be listed here.

Abstract

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.

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