%0 Journal Article
%A Fahlke, Christoph
%A Balandin, Taras
%A Astashkin, Roman
%A Alleva, Claudia
%A Machtens, Jan-Philipp
%A Gordeliy, Valentin
%A Baeken, Christian
%A Kovalev, Kirill
%A Berndt, Meike
%T Na + -dependent gate dynamics and electrostatic attraction ensure substrate coupling in glutamate transporters
%J Science advances
%V 6
%N 47
%@ 2375-2548
%C Washington, DC [u.a.]
%I Assoc.
%M FZJ-2020-03832
%P eaba9854 -
%D 2020
%X Excitatory amino acid transporters (EAATs) harness [Na+], [K+], and [H+] gradients for fast and efficient glutamate removal from the synaptic cleft. Since each glutamate is cotransported with three Na+ ions, [Na+] gradients are the predominant driving force for glutamate uptake. We combined all-atom molecular dynamics simulations, fluorescence spectroscopy, and x-ray crystallography to study Na+:substrate coupling in the EAAT homolog GltPh. A lipidic cubic phase x-ray crystal structure of wild-type, Na+-only bound GltPh at 2.5-Å resolution revealed the fully open, outward-facing state primed for subsequent substrate binding. Simulations and kinetic experiments established that only the binding of two Na+ ions to the Na1 and Na3 sites ensures complete HP2 gate opening via a conformational selection-like mechanism and enables high-affinity substrate binding via electrostatic attraction. The combination of Na+-stabilized gate opening and electrostatic coupling of aspartate to Na+ binding provides a constant Na+:substrate transport stoichiometry over a broad range of neurotransmitter concentrations.
%F PUB:(DE-HGF)16
%9 Journal Article
%$ pmid:33208356
%U <Go to ISI:>//WOS:000592173500003
%R 10.1126/sciadv.aba9854
%U https://juser.fz-juelich.de/record/885449