Retina-specific kinase involved in the signal turnoff via phosphorylation of rhodopsin (RHO), the G protein- coupled receptor that initiates the phototransduction cascade (By similarity). 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 (By similarity). Inhibition is calcium-dependent (By similarity). Interacts (via N-terminus) with RCVRN (via C-terminus); the interaction is Ca(2+)-dependent (By similarity). Interacts (when prenylated) with PDE6D; this promotes release from membranes (By similarity). May form a complex composed of RHO, GRK1 and RCVRN in a Ca(2+)-dependent manner; RCVRN prevents the interaction between GRK1 and RHO (By similarity). Subcellular location is not affected by light or dark conditions. Detected in retina (at protein level) (PubMed:21504899). Retina-specific. Expressed in rod and cone photoreceptor cells. Autophosphorylated, Ser-21 is a minor site of autophosphorylation compared to Ser-491 and Thr-492 (By similarity). Phosphorylation at Ser-21 is regulated by light and activated by cAMP. Farnesylation is required for full activity. Belongs to the protein kinase superfamily. AGC Ser/Thr protein kinase family. GPRK subfamily.