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Catalytic domain of Class III Phosphoinositide 3-kinase PI3Ks catalyze the transfer of the gamma-phosphoryl group from ATP to the 3-hydroxyl of the inositol ring of D-myo-phosphatidylinositol (PtdIns) or its derivatives. Class III PI3Ks, also called Vps34 (vacuolar protein sorting 34), contain an N-terminal lipid binding C2 domain, a PI3K homology domain of unknown function, and a C-terminal ATP-binding cataytic domain. They phosphorylate only the substrate PtdIns. They interact with a regulatory subunit, Vps15, to form a membrane-associated complex. Class III PI3Ks are involved in protein and vesicular trafficking and sorting, autophagy, trimeric G-protein signaling, and phagocytosis. PI3Ks play an important role in a variety of fundamental cellular processes, including cell motility, the Ras pathway, vesicle trafficking and secretion, immune cell activation and apoptosis. They can be divided into three main classes (I, II, and III), defined by their substrate specificity, regulation, and domain structure. The PI3K catalytic domain family is part of a larger superfamily that includes the catalytic domains of other kinases such as the typical serine/threonine/tyrosine protein kinases (PKs), aminoglycoside phosphotransferase, choline kinase, and RIO kinases. |
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