Catalytic domain of Fungal Nak1-like Serine/Threonine Kinases
STKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. This subfamily is composed of Schizosaccharomyces pombe Nak1, Saccharomyces cerevisiae Kic1p (kinase that interacts with Cdc31p) and related proteins. Nak1 (also called N-rich kinase 1), is required by fission yeast for polarizing the tips of actin cytoskeleton and is involved in cell growth, cell separation, cell morphology and cell-cycle progression. Kic1p is required by budding yeast for cell integrity and morphogenesis. Kic1p interacts with Cdc31p, the yeast homologue of centrin, and phosphorylates substrates in a Cdc31p-dependent manner. The Nak1 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.