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Catalytic domain of the Serine/Threonine Kinases, Cyclin-Dependent protein Kinase 2 and 3 STKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. CDK2 is regulated by cyclin E or cyclin A. Upon activation by cyclin E, it phosphorylates the retinoblastoma (pRb) protein which activates E2F mediated transcription and allows cells to move into S phase. The CDK2/cyclin A complex plays a role in regulating DNA replication. CDK2, together with CDK4, also regulates embryonic cell proliferation. Despite these important roles, mice deleted for the cdk2 gene are viable and normal except for being sterile. This may be due to compensation provided by CDK1 (also called Cdc2), which can also bind cyclin E and drive the G1 to S phase transition. CDK3 is regulated by cyclin C and it phosphorylates pRB specifically during the G0/G1 transition. This phosphorylation is required for cells to exit G0 efficiently and enter the G1 phase. CDKs belong to a large family of STKs that are regulated by their cognate cyclins. Together, they are involved in the control of cell-cycle progression, transcription, and neuronal function. The CDK2/3 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. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",