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Catalytic domain of the Serine/Threonine Kinase, G protein-coupled Receptor Kinase 3 STKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. GRK3, also called beta-adrenergic receptor kinase 2 (beta-ARK2), is widely expressed in many tissues. It is involved in modulating the cholinergic response of airway smooth muscles, and also plays a role in dopamine receptor regulation. GRK3-deficient mice show a lack of olfactory receptor desensitization and altered regulation of the M2 muscarinic airway. GRK3 promoter polymorphisms may also be associated with bipolar disorder. GRK3 contains an N-terminal RGS homology (RH) domain, a central catalytic domain, and C-terminal pleckstrin homology (PH) domain that mediates PIP2 and G protein betagamma-subunit translocation to the membrane. 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. The GRK3 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. |
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