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Catalytic domain of the Serine/Threonine Kinase, C-Raf (Rapidly Accelerated Fibrosarcoma) kinase STKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. C-Raf, also known as Raf-1 or c-Raf-1, is ubiquitously expressed and was the first Raf identified. It was characterized as the acquired oncogene from an acutely transforming murine sarcoma virus (3611-MSV) and the transforming agent from the avian retrovirus MH2. C-Raf-deficient mice embryos die around midgestation with increased apoptosis of embryonic tissues, especially in the fetal liver. One of the main functions of C-Raf is restricting caspase activation to promote survival in response to specific stimuli such as Fas stimulation, macrophage apoptosis, and erythroid differentiation. C-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 C-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.
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