SUBSTRATE TRANSPORT AND COCAINE BINDING OF HUMAN DOPAMINE TRANSPORTERIS REDUCED BY SUBSTITUTION OF CARBOXYL TAIL WITH THAT OF BOVINE DOPAMINE TRANSPORTER

A chimeric dopamine transporter (DAT) cDNA encoding mutant human DAT ( hDAT) protein in which the intracellular carboxyl-terminal tail is rep laced by that of the bovine dopamine transporter (bDAT) was constructe d. The chimeric hDAT cDNA was expressed in COS-7 cells, and [H-3]dopam ine and [H-3]MPP+ uptake and [H-3]CFT binding capacities were assessed . Substrate transport and ligand binding of bDAT were reduced by 32-43 % as a result of substitution of the carboxyl tail in hDAT, suggesting that the functional characteristics of bDAT arise from differences in the carboxyl tail between human and bovine DAT. Thus, it appears that the sequences encoded within the carboxyl terminal of DAT would be on e of the important determinants for its functions.