= Cyclin B
{wiki}
<Cyclin B> is a regulatory <protein> partner of <CDK1>. The <protein kinase> catalytic component is <CDK1>; bound <cyclin B> helps make that component competent to act. Changes in <cyclin B> synthesis and destruction regulate how much assembly can form, while <CDK1 phosphorylation states> determine whether bound assemblies are inhibited. This separates the supply of regulatory partners from release of an already assembled brake.<Molecular Biology of the Cell, 4th edition by Bruce Alberts and others/Components of the Cell-Cycle Control System>[Components of the Cell-Cycle Control System: cyclically activated protein kinases, Figures 17-15–17-17, and “Cdk Activity Can Be Suppressed Both by Inhibitory Phosphorylation and by Inhibitory Proteins”]{ref}
More <cyclin B> therefore need not give a proportional increase in <CDK1> activity. Compare the matched-input <cell-cycle hysteresis experiment>, where different histories produced different activities, and the distinct measurements under <CDK1 activity and protein abundance>. Neither comparison makes <cyclin B> itself the catalytic <protein kinase>.
Back to article page
