Molecular cloning and characterisation of a novel GABAB-related G-protein coupled receptor

Abstract Using a homology-based bioinformatics approach we have analysed human genomic sequence and identified the human and rodent orthologues of a novel putative seven transmembrane G protein coupled receptor, termed GABA BL . The amino acid sequence homology of these cDNAs compared to GABA B1 and GABA B2 led us to postulate that GABA BL was a putative novel GABA B receptor subunit. The C-terminal sequence of GABA BL contained a putative coiled-coil domain, di-leucine and several RXR(R) ER retention motifs, all of which have been shown to be critical in GABA B receptor subunit function. In addition, the distribution of GABA BL in the central nervous system was reminiscent of that of the other known GABA B subunits. However, we were unable to detect receptor function in response to any GABA B ligands when GABA BL was expressed in isolation or in the presence of either GABA B1 or GABA B2 . Therefore, if GABA BL is indeed a GABA B receptor subunit, its partner is a potentially novel receptor subunit or chaperone protein which has yet to be identified.