Catalytic domain of Fyn-related kinase-like Protein Tyrosine Kinases
PTKs catalyze the transfer of the gamma-phosphoryl group from ATP to tyrosine (tyr) residues in protein substrates. Frk and Srk are members of the Src subfamily of proteins, which are cytoplasmic (or non-receptor) PTKs. Frk, also known as Rak, is specifically expressed in liver, lung, kidney, intestine, mammary glands, and the islets of Langerhans. Rodent homologs were previously referred to as GTK (gastrointestinal tyr kinase), BSK (beta-cell Src-like kinase), or IYK (intestinal tyr kinase). Studies in mice reveal that Frk is not essential for viability. It plays a role in the signaling that leads to cytokine-induced beta-cell death in Type I diabetes. It also regulates beta-cell number during embryogenesis and early in life. Src kinases contain an N-terminal SH4 domain with a myristoylation site, followed by SH3 and SH2 domains, a tyr kinase domain, and a regulatory C-terminal region containing a conserved tyr. They are activated by autophosphorylation at the tyr kinase domain, but are negatively regulated by phosphorylation at the C-terminal tyr by Csk (C-terminal Src Kinase). The Frk-like subfamily is part of a larger superfamily that includes the catalytic domains of other kinases such as serine/threonine kinases, RIO kinases, aminoglycoside phosphotransferase, choline kinase, and phosphoinositide 3-kinase.
Comment:includes ATP binding and substrate binding sites
Comment:Based on the structures of other PTK family members bound to substrate peptides and ATP analogs as well as structures of Src subfamily PTKs bound with inhibitors and ATP analogs.
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