GRK1/RHOK

GRK1, historically named rhodopsin kinase, is the most specialised member of the visual GRK1/GRK7 subfamily. Expressed in rod photoreceptor outer segments, it phosphorylates light-activated rhodopsin on serine and threonine residues of the rhodopsin C-terminal tail, licensing arrestin binding and terminating phototransduction. Its activity toward non-visual receptors is very low, separating it from the broadly acting BARK-type kinases. A calcium-myristoyl switch operated by recoverin controls GRK1, which is N-terminally palmitoylated for membrane anchoring. Inactivating mutations in the human gene cause congenital stationary night blindness with abnormal electroretinogram responses. Recombinant GRK1 is used in phototransduction biochemistry, arrestin-recruitment assays and studies of this regulatory switch.