CDK7 Pathway - The T-loop

The T-loop

In order to be active, most CDKs require not only a cyclin partner but also phosphorylation at one particular site, which corresponds to Thr161 in human CDK1, and which is located within the so-called T-loop of kinase subdomain VIII. CDKl, CDK2 and CDK4 all require T-loop phosphorylation for maximum activity.