Catalytic domain of Mitogen-activated protein kinase kinase kinase kinase (MAP4K) 3-like Serine/Threonine Kinases
STKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. This subfamily includes MAP4K3, MAP4K1, MAP4K2, MAP4K5, and related proteins. Vertebrate members contain an N-terminal catalytic domain and a C-terminal citron homology (CNH) regulatory domain. MAP4K1, also called haematopoietic progenitor kinase 1 (HPK1), is a hematopoietic-specific STK involved in many cellular signaling cascades including MAPK, antigen receptor, apoptosis, growth factor, and cytokine signaling. It participates in the regulation of T cell receptor signaling and T cell-mediated immune responses. MAP4K2 was referred to as germinal center (GC) kinase because of its preferred location in GC B cells. MAP4K3 plays a role in the nutrient-responsive pathway of mTOR (mammalian target of rapamycin) signaling. It 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. MAP4K5, also called germinal center kinase-related enzyme (GCKR), has been shown to activate the MAPK c-Jun N-terminal kinase (JNK). The MAP4K3-like 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.
Jiyao W et al.(2023). "The conserved domain database in 2023.",