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Article Dans Une Revue Science Advances Année : 2020

Na+-dependent gate dynamics and electrostatic attraction ensure substrate coupling in glutamate transporters.

Résumé

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.
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Dates et versions

hal-03023502 , version 1 (25-11-2020)

Identifiants

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C Alleva, Kirill Kovalev, R Astashkin, M Berndt, C Baeken, et al.. Na+-dependent gate dynamics and electrostatic attraction ensure substrate coupling in glutamate transporters.. Science Advances , 2020, 6 (47), ⟨10.1126/sciadv.aba9854⟩. ⟨hal-03023502⟩
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