Phosphorylation of teleost phosducins and its effect on the affinity to G-protein beta gamma subunits

Abstract

Phosducin (PD) is a regulatory protein involved in the phototransduction cascade of vertebrate photoreceptor cells. We have previously demonstrated that there are rod- and cone-specific PDs (OlPD-R and OlPD-C) in the retina of the teleost fish, medaka (Oryzias latipes) [FEBS Lett. 502 (2001) 117]. A 6× His affinity precipitation assay revealed that phosphorylation by either protein kinase A (PKA) or Ca2+/calmodulin-dependent kinase II (CaMKII) reduced the affinity of recombinant medaka PDs to endogenous medaka G-protein beta gamma subunits (Gβγ). These results suggest that the affinity of medaka PDs to Gβγ is regulated by cAMP and Ca2+ concentrations as also found for mammalian PDs. However, we found a specific difference in the phosphorylation patterns between recombinant OlPD-R and OlPD-C, which resulted in different affinities to Gβγ. These differences may affect the light/dark-adaptation between medaka rods and cones.