Coupling of photoexcited rhodopsin to inositol phospholipid hydrolysis in fly photoreceptors

摘要: Abstract Fly photoreceptor membranes were used to test the effect on defined biochemical reactions of light and compounds causing excitation. Complementary electrophysiological studies examined whether putative second messengers excite fly cells. This analysis revealed following sequence events: photoexcited rhodopsin activates a G protein by facilitating GTP binding. The then phospholipase C that generates inositol trisphosphate, which in turn acts as an internal messenger bring about depolarization cell. Binding assays analogs measurements GTPase activity showed there are 1.6 million copies per binding component is 41-kDa protein, light-activated dependent photoconversion metarhodopsin. Analysis this enzyme under stringent control major product formed rapidly hydrolyzed specific phosphomonoesterase. Introduction trisphosphate intact cell mimics light, bisphosphoglycerate, inhibits hydrolysis, enhances effects dim light. interaction with thus similar both vertebrate invertebrate photoreceptors. These proteins, however, activate different enzymes: invertebrates cGMP phosphodiesterase vertebrates.