Catalytic domain of the Serine/Threonine Kinases, fungal Bck1-like Mitogen-Activated Protein Kinase Kinase Kinases
STKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. Members of this group include the MAPKKKs Saccharomyces cerevisiae Bck1 and Schizosaccharomyces pombe Mkh1, and related proteins. Budding yeast Bck1 is part of the cell integrity MAPK pathway, which is activated by stresses and aggressions to the cell wall. The MAPKKK Bck1, MAPKKs Mkk1 and Mkk2, and the MAPK Slt2 make up the cascade that is important in the maintenance of cell wall homeostasis. Fission yeast Mkh1 is involved in MAPK cascades regulating cell morphology, cell wall integrity, salt resistance, and filamentous growth in response to stress. MAPKKKs phosphorylate and activate MAPK kinases, which in turn phosphorylate and activate MAPKs during signaling cascades that are important in mediating cellular responses to extracellular signals. The Bck1 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.",