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Catalytic domain of the Serine/Threonine Kinase, A-Raf (Rapidly Accelerated Fibrosarcoma) kinase STKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. A-Raf cooperates with C-Raf in regulating ERK transient phosphorylation that is associated with cyclin D expression and cell cycle progression. Mice deficient in A-Raf are born alive but show neurological and intestinal defects. A-Raf demonstrates low kinase activity to MEK, compared with B- and C-Raf, and may also have alternative functions other than in the ERK signaling cascade. It regulates the M2 type pyruvate kinase, a key glycolytic enzyme. It also plays a role in endocytic membrane trafficking. A-Raf is a mitogen-activated protein kinase kinase kinase (MAP3K, MKKK, MAPKKK), which phosphorylates and activates MAPK kinases (MAPKKs or MKKs or MAP2Ks), which in turn phosphorylate and activate MAPKs during signaling cascades that are important in mediating cellular responses to extracellular signals. It functions in the linear Ras-Raf-MEK-ERK pathway that regulates many cellular processes including cycle regulation, proliferation, differentiation, survival, and apoptosis. The A-Raf 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.",