ABOLITION OF SUBSTRATE-DEPENDENT CURRENTS BY TYROSINE MUTATION IN THETRANSMEMBRANE DOMAIN OF GLUTAMATE TRANSPORTER

By site-directed mutagenesis we examined the roles of tyrosine residue s (Tyr(127)) in the putative transmembrane domain of rat glutamate tra nsporter (GLAST). When expressed in Xenopus oocytes, Y127F mutant prot ein, which was localized in plasma membranes of oocytes, completely ab olished glutamate uptake currents but did not affect the intrinsic sub strate-independent currents. Coexpression of wild type and mutant tran sporters supports that the Y127F mutation did not elicit glutamate eff lux. The efflux of glutamate by mild type or Y127F mutant transporters was measured under the condition of ion perturbation where transporte rs run in the reverse direction. (C) 1997 Federation of European Bioch emical Societies.