cd06645: STKc_MAP4K3 (this model, PSSM-Id:132976 is obsolete and has been replaced by 270812)
Catalytic domain of the Protein Serine/Threonine Kinase, Mitogen-activated protein kinase kinase kinase kinase 3
Serine/threonine kinases (STKs), mitogen-activated protein kinase (MAPK) kinase kinase kinase 3 (MAPKKKK3 or MAP4K3) subfamily, catalytic (c) domain. STKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. The MAP4K3 subfamily is part of a larger superfamily that includes the catalytic domains of other protein STKs, protein tyrosine kinases, RIO kinases, aminoglycoside phosphotransferase, choline kinase, and phosphoinositide 3-kinase. Members of this subfamily contain an N-terminal catalytic domain and a C-terminal citron homology (CNH) regulatory domain, similar to MAP4K4/6. MAP4Ks are involved in some MAPK signaling pathways that are important in mediating cellular responses to extracellular signals by activating a MAPK kinase kinase (MAPKKK or MAP3K or MKKK). Each MAPK cascade is activated either by a small GTP-binding protein or by an adaptor protein, which transmits the signal either directly to a MAP3K to start the triple kinase core cascade or indirectly through a mediator kinase, a MAP4K. MAP4K3 plays a role in the nutrient-responsive pathway of mTOR (mammalian target of rapamycin) signaling. MAP4K3 is required in the activation of S6 kinase by amino acids and for the phosphorylation of the mTOR-regulated inhibitor of eukaryotic initiation factor 4E. mTOR regulates ribosome biogenesis and protein translation, and is frequently deregulated in cancer.