catalytic activity:ATP + [G-protein-coupled receptor] = ADP + [G-protein-coupled receptor] phosphate.,function:Specifically phosphorylates the activated forms of G protein-coupled receptors. GRK4-alpha can phosphorylate rhodopsin and its activity is inhibited by calmodulin; the other three isoforms do not phosphorylate rhodopsin and do not interact with calmodulin.,similarity:Belongs to the protein kinase superfamily. AGC Ser/Thr protein kinase family. GPRK subfamily.,similarity:Contains 1 AGC-kinase C-terminal domain.,similarity:Contains 1 protein kinase domain.,similarity:Contains 1 RGS domain.,tissue specificity:Testis, and in a lower extent in other tissues including brain cortex and striatum.,
Cytoplasm. Cytoplasm, cell cortex. Both at the cell surface and dispersed in the cytoplasm under basal conditions. Receptor stimulation results in the internalization of GRK4 to the perinuclear area, where colocalization with DRD3 is observed strongly at 5 and 15 minutes. DRD3 and GRK4 colocalize in lipid rafts of renal proximal tubule cells.
Isoform 1, isoform 2, isoform 3, and isoform 4 are expressed in testis. Isoform 4 is expressed in myometrium.
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