CDK

CDK or Cyclin-dependent kinases are a family of protein kinases first discovered for their role in regulating the cell cycle. They are also involved in regulating transcription, mRNA processing, and the differentiation of nerve cells. They are present in all known eukaryotes, and their regulatory function in the cell cycle has been evolutionarily conserved. In fact, yeast cells can be made to progress through the cell cycle by inserting the genes for human cyclin-dependent kinases.

Function

CDKs are relatively small proteins, with molecular weights ranging from 34 to 40 kDa, and contain little more than the kinase domain. By contrast, mid to late G1 cyclin, G1/S cyclin, S cyclin, and M cyclin are all larger proteins (ranging from 45 to 90 kDa) and contain a conserved 150-amino acid cyclin box. The cyclin box folds into a compact alpha-helical structure that binds CDKs. A cyclin–CDK complex is also known as maturation-promoting factor (MPF).

Regulation

CDKs are regulated by several mechanisms such as cyclin binding, phosphorylation, and CDK inhibitor proteins. CDKs are inactive in the absence of the appropriate cyclin, and not all cyclins are expressed at the same time. Cyclins are produced or degraded in response to specific extracellular signals, leading to oscillations in cyclin concentrations during the cell cycle.

Clinical significance

CDKs are potential targets for cancer therapy due to their pivotal roles in cell cycle regulation. Several inhibitors of CDKs have been identified, and are being developed as anti-cancer drugs.

See also

• Cyclin
• Cell cycle
• Protein kinase
• Cancer therapy

CDK Resources
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