Interaction of GTP-binding protein Gq with photoactivated rhodopsin in the photoreceptor membranes of crayfish

AbstractInteraction of G-protein with photoactivated rhodopsin (Rh∗) in crayfish photoreceptor membranes was investigated by immunoprecipitation using an antibody against rhodopsin. Two kinds of protein were co-precipitated with rhodopsin. One is an α subunit of class-q G-protein (42 kDa, CGqα) which showed light-induced, dose-dependent binding to rhodopsin, and the other is an actin-like protein (44 kDa) with light-independent binding. Most of the CGqα was available for binding to Rh∗ but was dissociated from Rh∗ in the presence of GTPγS. These findings demonstrate that, in the crayfish photoreceptor, a Gq class of G-protein is activated by Rh∗