Specifically phosphorylates the activated forms of G protein-coupled receptors. Such receptor phosphorylation initiates beta-arrestin-mediated receptor desensitization, internalization, and signaling events leading to their desensitization. Seems to be involved in the desensitization of D2-like dopamine receptors in striatum and chemokine receptor CXCR4 which is critical for CXCL12-induced cell chemotaxis (By similarity). Phosphorylates rhodopsin (RHO) (in vitro) and a non G-protein-coupled receptor: LRP6 during Wnt signaling (in vitro). [G-protein-coupled receptor] + ATP = [G-protein-coupled receptor]-phosphate + ADP + H(+) Interacts with GIT1. Widely expressed. It is uncertain whether palmitoylation is on Cys-561 and/or Cys-562 and/or Cys-565. Belongs to the protein kinase superfamily. AGC Ser/Thr protein kinase family. GPRK subfamily.