title: Mutation of an amino acid residue influencing potassium coupling in the glutamate transporter GLT-1 induces obligate exchange.
abstract: Glutamate transporters maintain low synaptic concentrations of neurotransmitter by coupling uptake to flux of other ions. After cotransport of glutamic acid with Na+, the cycle is completed by countertransport of K+. We have identified an amino acid residue (glutamate 404) influencing ion coupling in a domain of the transporter implicated previously in kainate binding. Mutation of this residue to aspartate (E404D) prevents both forward and reverse transport induced by K+. Sodium-dependent transmitter exchange and a transporter-mediated chloride conductance are unaffected by the mutation, indicating that this residue selectively influences potassium flux coupling. The results support a kinetic model in which sodium and potassium are translocated in distinct steps and suggest that this highly conserved region of the transporter is intimately associated with the ion permeation pathway.
authors.affiliation: Vollum Institute, Oregon Health Sciences University, Portland, Oregon 97201, USA.
authors.forename: M P
authors.initials: MP
authors.lastname: Kavanaugh
authors.forename: A
authors.initials: A
authors.lastname: Bendahan
authors.forename: N
authors.initials: N
authors.lastname: Zerangue
authors.forename: Y
authors.initials: Y
authors.lastname: Zhang
authors.forename: B I
authors.initials: BI
authors.lastname: Kanner
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism*; D027322:Amino Acid Transport System X-AG; D000818:Animals; D001692:Biological Transport; D006367:HeLa Cells; D006801:Humans; D016297:Mutagenesis, Site-Directed; D011188:Potassium / Q000378:metabolism*; D051381:Rats
chemical_list: D018528:ATP-Binding Cassette Transporters; D027322:Amino Acid Transport System X-AG; D011188:Potassium