Cyclic nucleotides and GTP analogues stimulate light-induced phosphorylation of octopus rhodopsin.

Light-induced phosphorylation of octopus rhodopsin in microvillar membrane was shown to be stimulated by cyclic nucleotides in contrast to vertebrate rhodopsin kinase. Non-hydrolyzable GTP analogues, GTP lambda S and GppNHp, greatly enhanced the light-induced phosphorylation of octopus rhodopsin, but the non-hydrolyzable GDP analogue, GDP beta S, was not effective. These results suggest that rhodopsin A-kinase is involved in regulating the interaction between rhodopsin and G-protein in octopus photoreceptors.