Biochemistry, molecular genetics, and biology glossary terms for Companion Sites.

cyclin-dependent kinases

Cyclin-dependent kinases (CDKs) are a subclass of serine/threonine protein kinases that play a role in regulation of transcription and mRNA processing, and in regulation of the cell cycle. Specific protein kinases transfer a phosphate group from a donor such as ATP to amino acid acceptors in proteins, while protein phosphatases remove the phosphate groups that have been attached by protein kinases.

The activity of cyclin-dependent kinases is modulated by binding to cyclins, which are proteins so-named because their levels vary periodically during the cell cycle. The binding of cyclins to cyclin-dependent kinases regulates CDK activity, selecting the proteins to be phosphorylated. Although levels of CDK-molecules are constant during the cell cycle, their activities vary because of the regulatory function of the cyclins. Thus, periodic protein degradation is an important general control mechanism of the cell cycle.

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