Molecular Mechanisms of rhodopsin phosphorylation and dephosphorylation.

Abstract

Rhodopsin absorbs light and undergoes a photobleaching. Its intermediates activate a cGMP cascade that generates a hyperpolarized potential in rod photoreceptor cells. This light-triggered cascade reaction is terminated and completely restored to the dark levels by another enzymatically controlled reaction initiated by rhodopsin phosphorylation by rhodopsin kinase. Thus, phosphorylation and dephosphorylation of rhodopsin is a crucial regulatory mechanism of photoreception of rods. I found that rhodopsin phosphorylation predominantly occurs at 334, 338 and 343 serine residues in both in vivo and in vitro. Furthermore, I also found rhodopsin phosphorylation is involved in not only the quenching phototransduction but the dark adaptation processes.