GENE STRUCTURE AND CHROMOSOME LOCALIZATION OF THE G(GAMMA-C) SUBUNIT OF HUMAN CONE G-PROTEIN (GNGT2)

Phototransduction in the vertebrate rod and cone photoreceptors is reg ulated by structurally homologous and yet distinct groups of signaling proteins. We have previously identified in bovine retinas a cone-spec ific G-protein gamma subunit (G(gamma c), previously named G(gamma 8)) , which may play a key role in coupling the cone visual pigment to pho sphodiesterase (O. C. Ong ct al., 1995, J. Biol. Chem. 270: 8495-8500) . We report here the characterization of human G(gamma c) and its gene structure. Human G(gamma c) subunit shares a high degree of sequence identity with the corresponding bovine G(gamma c) isoform (85%) and hu man rod G(gamma 1) (63%). The protein is specifically localized in con es, as indicated by immunohistochemical staining using anti-G(gamma c) antibodies. Nucleotide sequence analysis of the G(gamma c) gene (GNGT 2) reveals a structure consisting of three exons and two introns, with the intron splice sites similar to that of the rod G(gamma 1) gene (G NGT1). By using fluorescence in situ hybridization, we have further lo calized the human GNGT2 gene to chromosome 17q21. The elucidation of t he G(gamma c) gene structure would facilitate the identification of ge netic defects associated with cone degeneration, (C) 1997 Academic Pre ss.