MOLECULAR-CLONING AND STRUCTURE OF THE HUMAN (GABATHG) GABA TRANSPORTER GENE

A cDNA molecule encoding the human GABA transporter was synthesized by means of polymerase chain reaction (PCR) technique and used as probe for selecting a human genomic DNA fragment encoding GABA transporter. A positive clone harboring the whole gene was obtained from a human ly mphocyte genomic library through utilizing the genomic 'walking' techn ique. The clone, designated as pHGAT, harbours a DNA fragment of about 39 kb in length inserted into the BamHI site in cosmid pWE15. The gen e covers about 25 kb in length and is constituted by four EcoRI restri cted fragments which are 13.7 kb, 3.1 kb, 4.2 kb and 7.2 kb long, resp ectively. The genomic clone contains 15 introns, including two introns prior to the initiator methionine (i.e., the translation start site i s in exon 3). Eleven exons encode the twelve transmembrane regions in the transporter protein. Thus as is the case for a number of other mem brane proteins, there appears to be a strong tendency for the putative transmembrane domains to be encoded by separate exons. It is noted th at the structure of the human GABA transporter gene reported here diff ers from the mouse gene which is contains 12 introns.