Catalytic domain of fungal Pek1-like dual-specificity Mitogen-Activated Protein Kinase Kinases
PKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine (ST) or tyrosine residues on protein substrates. Members of this group include the MAPKKs Pek1/Skh1 from Schizosaccharomyces pombe and MKK2 from Saccharomyces cerevisiae, and related proteins. Both fission yeast Pek1 and baker's yeast MKK2 are components of the cell integrity MAPK pathway. In fission yeast, Pek1 phosphorylates and activates Pmk1/Spm1 and is regulated by the MAPKK kinase Mkh1. In baker's yeast, the pathway involves the MAPK Slt2, the MAPKKs MKK1 and MKK2, and the MAPKK kinase Bck1. The cell integrity MAPK cascade is activated by multiple stress conditions, and is essential in cell wall construction, morphogenesis, cytokinesis, and ion homeostasis. MAPK signaling pathways are important mediators of cellular responses to extracellular signals. 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.
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