P. Kunapuli et Jl. Benovic, CLONING AND EXPRESSION OF GRK5 - A MEMBER OF THE G-PROTEIN-COUPLED RECEPTOR KINASE FAMILY, Proceedings of the National Academy of Sciences of the United Statesof America, 90(12), 1993, pp. 5588-5592
Guanine nucleotide binding protein (G-protein)-coupled receptor kinase
s (GRKs) specifically phosphorylate the agonist-occupied form of G-pro
tein-coupled receptors such as the beta2-adrenergic receptor and rhodo
psin. The best characterized members of this family include the beta-a
drenergic receptor kinase (betaARK) and rhodopsin kinase. To identify
additional members of the GRK family, the polymerase chain reaction wa
s used to amplify human heart cDNA using degenerate oligonucleotide pr
imers from highly conserved regions unique to the GRK family. Here we
report the isolation of a cDNA that encodes a 590-amino acid protein k
inase, termed GRK5, which has 34.8% and 47.2% amino acid identities wi
th betaARK and rhodopsin kinase, respectively. Interestingly, GRK5 has
an even higher homology with Drosophila GPRK-2 (71.0% identity) and t
he recently identified human IT11 (69.1 % identity). Northern blot ana
lysis of GRK5 with selected human tissues reveals a message of almost-
equal-to 3 kilobases with highest levels in heart, placenta, lung > sk
eletal muscle > brain, liver, pancreas > kidney. GRK5, overexpressed i
n Sf9 insect cells using the baculovirus system, was able to phosphory
late rhodopsin in a light-dependent manner. In addition, GRK5 neither
contains a consensus sequence for isoprenylation like rhodopsin kinase
nor is activated by G-protein betagamma subunits like betaARK1. Thus,
GRK5 represents a member of the GRK family that likely has a unique p
hysiological role.