Retina-specific kinase involved in the signal turnoff via phosphorylation of rhodopsin (RHO), the G protein- coupled receptor that initiates the phototransduction cascade (PubMed:12686556, PubMed:16675451, PubMed:21299498). This rapid desensitization is essential for scotopic vision and permits rapid adaptation to changes in illumination (By similarity). May play a role in the maintenance of the outer nuclear layer in the retina (By similarity). ATP + L-threonyl-[rhodopsin] = ADP + H(+) + O-phospho-L-threonyl-[rhodopsin] ATP + L-seryl-[rhodopsin] = ADP + H(+) + O-phospho-L-seryl-[rhodopsin] Inhibited by RCVRN, which prevents the interaction between GRK1 and RHO (PubMed:12686556, PubMed:21299498). Inhibition is calcium-dependent (PubMed:12686556). Interacts (via N-terminus) with RCVRN (via C-terminus); the interaction is Ca(2+)-dependent (PubMed:16675451, PubMed:17020884, PubMed:21299498, PubMed:24189072, PubMed:26584024). Interacts (when prenylated) with PDE6D; this promotes release from membranes (PubMed:14561760). May form a complex composed of RHO, GRK1 and RCVRN in a Ca(2+)-dependent manner; RCVRN prevents the interaction between GRK1 and RHO (PubMed:17020884). Subcellular location is not affected by light or dark conditions. Rod outer segments of retina photoreceptor cells (at protein level) (PubMed:1656454, PubMed:1730692, PubMed:1527025). Retina (PubMed:1656454). Autophosphorylated, Ser-21 is a minor site of autophosphorylation compared to Ser-488 and Thr-489. Phosphorylation at Ser-21 is regulated by light and activated by cAMP (Probable). Farnesylation is required for full activity. Belongs to the protein kinase superfamily. AGC Ser/Thr protein kinase family. GPRK subfamily.