Chloride Binding Site of Neurotransmitter Sodium Symporters

Overview

Journal Proc Natl Acad Sci U S A

Specialty Science

Date 2013 May 4

PMID 23641004

Citations 61

Authors

Adriana K Kantcheva

Matthias Quick

Lei Shi

Anne-Marie Lund Winther

Sebastian Stolzenberg

Harel Weinstein

Jonathan A Javitch

Poul Nissen

Affiliations

Soon will be listed here.

Abstract

Neurotransmitter:sodium symporters (NSSs) play a critical role in signaling by reuptake of neurotransmitters. Eukaryotic NSSs are chloride-dependent, whereas prokaryotic NSS homologs like LeuT are chloride-independent but contain an acidic residue (Glu290 in LeuT) at a site where eukaryotic NSSs have a serine. The LeuT-E290S mutant displays chloride-dependent activity. We show that, in LeuT-E290S cocrystallized with bromide or chloride, the anion is coordinated by side chain hydroxyls from Tyr47, Ser290, and Thr254 and the side chain amide of Gln250. The bound anion and the nearby sodium ion in the Na1 site organize a connection between their coordinating residues and the extracellular gate of LeuT through a continuous H-bond network. The specific insights from the structures, combined with results from substrate binding studies and molecular dynamics simulations, reveal an anion-dependent occlusion mechanism for NSS and shed light on the functional role of chloride binding.

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