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Catalytic domain of the dual-specificity Protein Kinase, Mitogen-Activated Protein Kinase Kinase PKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine (ST) or tyrosine residues on protein substrates. MAPKKs are dual-specificity PKs that phosphorylate their downstream targets, MAPKs, at specific threonine and tyrosine residues. The MAPK signaling pathways are important mediators of cellular responses to extracellular signals. The pathways involve a triple kinase core cascade comprising the MAPK, which is phosphorylated and activated by a MAPK kinase (MAPKK or MKK or MAP2K), which itself is phosphorylated and activated by a MAPKK kinase (MAPKKK or MKKK or MAP3K). There are three MAPK subfamilies: extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and p38. In mammalian cells, there are seven MAPKKs (named MKK1-7) and 20 MAPKKKs. Each MAPK subfamily can be activated by at least two cognate MAPKKs and by multiple MAPKKKs. The MAPKK 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.",