Catalytic domain of fungal PBS2-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 Polymyxin B resistance protein 2 (PBS2) from Saccharomyces cerevisiae, Wis1 from Schizosaccharomyces pombe, and related proteins. PBS2 and Wis1 are components of stress-activated MAPK cascades in budding and fission yeast, respectively. PBS2 is the specific activator of the MAPK Hog1, which plays a central role in the response of budding yeast to stress including exposure to arsenite and hyperosmotic environments. Wis1 phosphorylates and activates the MAPK Sty1 (also called Spc1 or Phh1), which stimulates a transcriptional response to a wide range of cellular insults through the bZip transcription factors Atf1, Pcr1, and Pap1. The PBS2 subfamily is part of a larger superfamily that includes the catalytic domains of STKs, protein tyrosine kinases, RIO kinases, aminoglycoside phosphotransferase, choline kinase, and phosphoinositide 3-kinase.