Catalytic domain of the dual-specificity Protein Kinases, Mitogen-activated protein Kinase Kinases 3 and 6
PKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine (ST) or tyrosine residues on protein substrates. MKK3 and MKK6 are dual-specificity PKs that phosphorylate and activate their downstream target, p38 MAPK, on specific threonine and tyrosine residues. MKK3/6 play roles in the regulation of cell cycle progression, cytokine- and stress-induced apoptosis, oncogenic transformation, and adult tissue regeneration. In addition, MKK6 plays a critical role in osteoclast survival in inflammatory disease while MKK3 is associated with tumor invasion, progression, and poor patient survival in glioma. The MKK3/6 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.