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Catalytic domain of the Dual-specificity protein kinase, Myt1 Dual-specificity PKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine as well as tyrosine residues on protein substrates. Myt1 is a cytoplasmic cell cycle checkpoint kinase that can keep the cyclin-dependent kinase CDK1 in an inactive state through phosphorylation of N-terminal thr (T14) and tyr (Y15) residues, leading to the delay of meiosis I entry. Meiotic progression is ensured by a two-step inhibition and downregulation of Myt1 by CDK1/XRINGO and p90Rsk during oocyte maturation. In addition, Myt1 targets cyclin B1/B2 and is essential for Golgi and ER assembly during telophase. In Drosophila, Myt1 may be a downstream target of Notch during eye development. The Myt1 subfamily is part of a larger superfamily that includes the catalytic domains of other protein serine/threonine PKs, protein tyrosine kinases, RIO kinases, aminoglycoside phosphotransferase, choline kinase, and phosphoinositide 3-kinase.
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