High impact information on Gbeta76C

• Upon ligand binding, the transmitter receptors interact with heterotrimeric G proteins, allowing G alpha and G beta gamma subunits to disengage [1].
• We have isolated Drosophila melanogaster mutants defective in an eye-specific G-protein beta-subunit (G beta e), and show here that the beta-subunit is essential for G-protein-receptor coupling in vivo [2].
• An eye-specific G beta subunit essential for termination of the phototransduction cascade [2].
• Excess of Gbetae over Gqalphae in vivo prevents dark, spontaneous activity of Drosophila photoreceptors [3].
• G proteins of the Gq/11 subfamily functionally couple cell surface receptors to phospholipase C beta (PLC beta) isoforms [4].

Biological context of Gbeta76C

• Remarkably, all three nonvisual B exons are highly similar (82% identity at the amino acid level) to the Gq alpha family consensus, from Caenorhabditis elegans to human, but all three visual A exons are divergent (61% identity) [5].
• Although the role of the G alpha subunit in effector activation, guanine nucleotide exchange and GTP hydrolysis has been well studied, the cellular functions of the G beta subunits are less well understood [2].
• Tn-Gbeta shares approximately 90% amino acid sequence identity with Gbeta from Drosophila melanogaster and 84% identity with mammalian Gbeta (human Gbeta1) [6].

Associations of Gbeta76C with chemical compounds

• Reconstitution of purified GTPgammaS-bound soluble squid Gq with PLC-70 resulted in significant enhancement of PIP2 hydrolysis over a range of Ca2+ concentrations and shifted the maximum activation by calcium to 1 microM [7].

Physical interactions of Gbeta76C

• In the transgenic flies, mutated Ggammae forms a dimeric complex with Gbetae, with the consequence that the fraction of non-membrane-bound Gbetagamma is increased [8].
• G beta gamma dimers bind G alpha subunits and anchor them to the membrane for presentation to the receptor [2].

Regulatory relationships of Gbeta76C

• We have previously purified a 140-kDa PLC enzyme from squid photoreceptors that is regulated by squid Gq [7].

Other interactions of Gbeta76C

• Despite similarities in the primary structure between the transducin gamma subunit and Drosophila Ggammae, we observed no interaction of human Ggammarod with Drosophila Gbetae [8].
• A G protein beta subunit gene (Gbe) is expressed only in the eyes of adult D. melanogaster [9].
• These results suggest that cephalopod phototransduction is mediated by Gq activation of more than one cytosolic PLC enzyme [7].

Analytical, diagnostic and therapeutic context of Gbeta76C

• Novel Gq alpha isoform is a candidate transducer of rhodopsin signaling in a Drosophila testes-autonomous pacemaker [5].
• Immunocytochemical and in situ hybridization analyses further demonstrate that Gbe is expressed in the eyes but not in the brain, whereas Gbb is abundantly expressed in the brain [9].

References