Functional significance of N- and C-terminus of the amino acid transporters EAAC1 and ASCT1: characterization of chimeric transporters

To localize functionally significant domains in the amino acid transporters of mouse brain mEAAC1 and mASCT1, cRNA encoding for wild-type and chimeric transporters was injected into Xenopus oocytes. Activity of expressed tran sporters was investigated by measurements of uptake of H-3-labeled glutamat e and serine and of glutamate and serine-induced currents under voltage cla mp. Though all transporters accept glutamate and serine as substrate, the c entral part of the protein (Ala(94)-Met(418) of mEAAC1 and Ala(119)-Ile(393 ) of mASCT1) determines substrate selectivity. The C-terminus rectifies the interaction with the respective substrate. A channel mode of the glutamate transporter can be activated by glutamate and serine, and the N- and C-ter mini of the mEAAC1 seem to be essential for the channel formation. (C) 2000 Elsevier Science B.V. All rights reserved.