GRK1 is a member of the guanine nucleotide-binding protein (G protein)-coupled receptor kinase subfamily of the Ser/Thr protein kinases. GRK1 mediates rapid desensitization of rod photoreceptors to light by catalyzing phosphorylation of the visual pigment rhodopsin which leads to its deactivation. Defects in GRK1 are known to cause Oguchi disease 2 (also known as stationary night blindness Oguchi type-2). GRK1 can be phosphorylated by PKA and this reduces the ability of GRK1 to phosphorylate rhodopsin in vitro. It is speculated that phosphorylation of GRK1 by PKA in vivo occurs in the dark when cAMP levels in photoreceptor cells are elevated.
