Characterization of a putative gamma-aminobutyric acid (GABA) receptor beta subunit gene from Drosophila melanogaster.

A cDNA encoding a novel member of the ligand-gated chloride channel gene family of insects has been isolated from Drosophila melanogaster and characterized. The 1488 nucleotide open reading frame of this cDNA encodes an amino acid sequence having structural features conserved among ligand-gated chloride channel subunit proteins, including four hydrophobic domains capable of forming transmembrane helices (M1-M4), an octapeptide "signature motif" occurring in M2, a large intracellular domain between M3 and M4, and cysteine residues postulated to form a disulfide-bridged loop structure in the extracellular domain. Among characterized members of this gene family, this gene exhibits the greatest similarity to GABA receptor beta subunit genes. This high level of structural similarity suggests that its encoded protein may be a functional homologue of the beta subunit family in the D. melanogaster nervous system.