Electrogenic steps associated with substrate binding to the neuronal glutamate transporter EAAC1

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dc.contributor.author Tanui, Rose
dc.contributor.author Tao, Zhen
dc.contributor.author Silverstein, Nechama
dc.contributor.author Kanner, Baruch
dc.contributor.author Grewer, Christof
dc.date.accessioned 2019-02-12T09:42:19Z
dc.date.available 2019-02-12T09:42:19Z
dc.date.issued 2016-04-04
dc.identifier.citation t http://www.jbc.org/cgi/doi/10.1074/jbc.M116.722470 en_US
dc.description.abstract Glutamate transporters actively take up glutamate into the cell, driven by the co-transport of sodium ions down their transmembrane concentration gradient. It was proposed that glutamate binds to its binding site and is subsequently transported across the membrane in the negatively charged form. With the glutamate binding site being located partially within the membrane domain, the possibility has to be considered that glutamate binding is dependent on the transmembrane potential, and, thus, electrogenic. Experiments presented in this report test this possibility. Rapid application of glutamate to the wild-type glutamate transporter subtype EAAC1 (excitatory amino acid carrier 1) through photo-release from caged glutamate generated a transient inward current, as expected for the electrogenic inward movement of cotransported Na+ . In contrast, glutamate application to a transporter with the mutation A334E induced transient outward current, consistent with movement of negatively-charged glutamate into its binding site within the dielectric of the membrane. These results are in agreement with electrostatic calculations, predicting a valence for glutamate binding of -0.27. Control experiments further validate and rule out other possible explanations for the transient outward current. Electrogenic glutamate binding can be isolated in the mutant glutamate transporter because reactions such as glutamate translocation and/or Na+ binding to the glutamate-bound state, are inhibited by the A334E substitution. Electrogenic glutamate binding has to be considered together with other voltage dependent partial reactions to cooperatively determine the voltage dependence of steady-state glutamate uptake and glutamate buffering at the synapse. en_US
dc.language.iso en en_US
dc.publisher The American Society for Biochemistry and Molecular Biology en_US
dc.subject Glutamate transporter, mutagenesis, electrophysiology, kinetics, mechanism, simulations en_US
dc.title Electrogenic steps associated with substrate binding to the neuronal glutamate transporter EAAC1 en_US
dc.type Article en_US

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