Distinct conformational states mediate the transport and anion channel properties of the glutamate transporter EAAT-1.
Glutamate transport by the excitatory amino acid transporters (EAATs) is coupled to the co-transport of 3 Na(+), 1 H(+), and the counter-transport of 1 K(+) ion. In addition to coupled ion fluxes, glutamate and Na(+) binding to the transporter activates a thermodynamically uncoupled anion conductance through the transporter. In this study, we have distinguished between these two conductance states of the EAAT-1 transporter using a [2-(trimethylammonium)ethyl]methanethiosulfonate-modified V452C mutant transporter. Glutamate binds to the modified mutant transporter and activates the uncoupled anion conductance but is not transported. The selective alteration of the transport function without altering the anion channel function of the V452C mutant transporter suggests that the two functions are generated by distinct conformational states of the transporter.
Ryan
Renae M
RM
Department of Pharmacology, University of Sydney, Sydney, New South Wales 2006, Australia.
Vandenberg
Robert J
RJ
D000818:Animals; D000838:Anions; D001692:Biological Transport; D018076:DNA, Complementary / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D027341:Excitatory Amino Acid Transporter 1 / Q000737:chemistry* / Q000378:metabolism*; D018698:Glutamic Acid / Q000378:metabolism*; D006801:Humans; D020128:Inhibitory Concentration 50; D007700:Kinetics; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D010957:Plasmids / Q000378:metabolism; D011188:Potassium / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D021381:Protein Transport; D013816:Thermodynamics; D014982:Xenopus laevis
D000838:Anions; D018076:DNA, Complementary; D027341:Excitatory Amino Acid Transporter 1; D018698:Glutamic Acid; D011188:Potassium