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Catalytic domain of the Serine/Threonine Kinase, G protein-coupled Receptor Kinase STKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. GRKs phosphorylate and regulate G protein-coupled receptors (GPCRs), the largest superfamily of cell surface receptors, which regulate some part of nearly all physiological functions. Phosphorylated GPCRs bind to arrestins, which prevents further G protein signaling despite the presence of activating ligand. GRKs play important roles in the cardiovascular, immune, respiratory, skeletal, and nervous systems. They contain a central catalytic domain, flanked by N- and C-terminal extensions. The N-terminus contains an RGS (regulator of G protein signaling) homology (RH) domain and several motifs. The C-terminus diverges among different groups of GRKs. There are seven types of GRKs, named GRK1 to GRK7, which are subdivided into three main groups: visual (GRK1/7); beta-adrenergic receptor kinases (GRK2/3); and GRK4-like (GRK4/5/6). Expression of GRK2/3/5/6 is widespread while GRK1/4/7 show a limited tissue distribution. The substrate spectrum of the widely expressed GRKs partially overlaps. The GRK subfamily is part of a larger superfamily that includes the catalytic domains of other STKs, protein tyrosine kinases, RIO kinases, aminoglycoside phosphotransferase, choline kinase, and phosphoinositide 3-kinase. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",