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Catalytic domain of the Serine/Threonine kinase, Oocyte maturation factor Mos STKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. Mos (or c-Mos) is a germ-cell specific kinase that plays roles in both the release of primary arrest and the induction of secondary arrest in oocytes. It is expressed towards the end of meiosis I and is quickly degraded upon fertilization. It is a component of the cytostatic factor (CSF), which is responsible for metaphase II arrest. In addition, Mos activates a phoshorylation cascade that leads to the activation of the p34 subunit of MPF (mitosis-promoting factor or maturation promoting factor), a cyclin-dependent kinase that is responsible for the release of primary arrest in meiosis I. The Mos subfamily is part of a larger superfamily that includes the catalytic domains of other protein STKs, protein tyrosine kinases, RIO kinases, aminoglycoside phosphotransferase, choline kinase, and phosphoinositide 3-kinase.
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