CDK, or cyclin-dependent kinases, is a set of Ser/Thr kinase systems corresponding to the cell cycle process. Various CDKs are activated alternately along the phase of the cell cycle, phosphorylating the corresponding substrates, allowing cell cycle events to proceed in an orderly manner. Cyclin-dependent protein kinases are a group of serine / threonine protein kinases. CDK drives the cell cycle through chemical action on serine / threonine proteins. Synergistically with cyclin cyclin, it is involved in cell cycle regulation. Important factor. CDK can combine with cyclin to form a heterodimer, where CDK is a catalytic subunit, cyclin is a regulatory subunit, and different cyclin-CDK complexes catalyze the phosphorylation of different substrates through CDK activity to achieve different cell cycle Phase advancement and transformation. The activity of CDK depends on the sequential expression of its positive regulatory subunit cyclin and the concentration of its negative regulatory subunit CKI (cyclin dependent kinase inhibitor). At the same time, CDK activity is also regulated by phosphorylation and dephosphorylation, as well as oncogenes and tumor suppressor genes.
Structure
In different CDK molecular structures, there is a similar kinase domain. This region has a conserved sequence, namely PSTAIRE (prosperisopropylisoleucine valley), which is a region that mediates the binding of kinases to cyclins. CDK has the activity of a kinase only when it binds to cyclin, which is called a cyclin-dependent kinase. Because Cdc2 was first discovered, and several other CDK kinases were obtained by comparison, Cdc2 kinase was named CDK1. Cdks has three important functional areas. The first functional domain is the binding site of ATP and the active part of the enzyme; the second functional domain is the binding site of the regulatory subunit (Cyclin); the third functional domain is the binding site of P13suc1 (P13suc1 can inhibit kinase activity and prevent cells Enter or exit period M). Various Cdk are activated at specific times in the cell cycle, driving cells through the cell cycle by phosphorylating substrates.
Functions
Activated CDK1 can phosphorylate target proteins and produce corresponding physiological effects, such as phosphorylation of nuclear lamin protein leading to nuclear fibril disintegration, disappearance of nuclear membrane, and phosphorylation of H1 leading to chromosome condensation. The net result of these effects is that the cell cycle runs continuously. Therefore, CDK kinases and their regulators are also called cell cycle engines.
Action steps
CyclinB generally begins to synthesize at the late stage of G1. Through S phase ↑, it reaches G2 phase, CyclinB content reaches a certain level, and enters the nucleus to bind to CDK1, so that CDK1 kinase activity begins to appear. The activity of CDK1 is closely related to the content of CyclinB. CDK1 activation can cause phosphorylation of nuclear laminin, depolymerization of nuclear laminar layer, disintegration of nuclear membrane, and phosphorylation of histone H1, coagulation of chromatin, phosphorylation of nucleoli, disintegration of nucleoli, and microtubule binding. The microtubules are rearranged and a mitosis is formed. When the cell exits the M phase, CyclinB is degraded, the kinase is inactivated, and various substrates are dephosphorylated, which promotes chromosome aggregation, nuclear membrane nucleoli reconstruction, and guides the cell into the G1 phase.
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