MOLECULAR-CLONING AND FUNCTIONAL-CHARACTERIZATION OF A GABA BETAINE TRANSPORTER FROM HUMAN KIDNEY

The human homologue of the canine GABA/betaine transporter (BGT-1) was isolated from a kidney inner medulla cDNA library, The coding sequenc e predicts a 614 amino acids protein with the typical features of neur otransmitter transporter family, The gene maps to chromosome 12p13 and , in addition to kidney, is also expressed in brain, liver, heart, ske letal muscle, and placenta. Functional studies reveal a K-m = 20 mu M for GABA transport and a coupling to Na+ and Cl- with a stoichiometry 3 Na+:2 Cl-:1 GABA, At 500 mu M the GABA transport was inhibited by va rious compounds with the following potency order: quinidine > verapami l > phloretin > betaine.