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Catalytic domain of the Protein Serine/Threonine Kinase, Microtubule-associated serine/threonine kinase STKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. MAST kinases contain an N-terminal domain of unknown function, a central catalytic domain, and a C-terminal PDZ domain that mediates protein-protein interactions. There are four mammalian MAST kinases, named MAST1-MAST4. MAST1 is also called syntrophin-associated STK (SAST) while MAST2 is also called MAST205. MAST kinases are cytoskeletal associated kinases of unknown function that are also expressed at neuromuscular junctions and postsynaptic densities. MAST1, MAST2, and MAST3 bind and phosphorylate the tumor suppressor PTEN, and may contribute to the regulation and stabilization of PTEN. MAST2 is involved in the regulation of the Fc-gamma receptor of the innate immune response in macrophages, and may also be involved in the regulation of the Na+/H+ exchanger NHE3. The MAST kinase 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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