THE RECEPTOR KINASE FAMILY - PRIMARY STRUCTURE OF RHODOPSIN KINASE REVEALS SIMILARITIES TO THE BETA-ADRENERGIC-RECEPTOR KINASE

Light-dependent deactivation of rhodopsin as well as homologous desensitization of beta-adrenergic receptors involves receptor phosphorylation that is mediated by the highly specific protein kinases rhodopsin kinase (RK) and beta-adrenergic receptor kinase (beta-ARK), respectively. We report here the cloning of a complementary DNA for RK. The deduced amino acid sequence shows a high degree of homology to beta-ARK. In a phylogenetic tree constructed by comparing the catalytic domains of several protein kinases, RK and beta-ARK are located on a branch close to, but separate from, the cyclic nucleotide-dependent protein kinase and protein kinase C subfamilies. From the common structural features we conclude that both RK and beta-ARK are members of a newly delineated gene family of guanine nucleotide-binding protein (G protein)-coupled receptor kinases that may function in diverse pathways to regulate the function of such receptors.