CDK1-cyclin B (Cyclin Dependent Kinase 1), also known as Cdc2-cyclin B (Cell division control protein kinase 2) or M-phase promoting factor (MPF), is a member of cyclin-dependent kinases implicated in cell cycle control in eukaryotes. Activation of the CDK1-cyclin B brings the onset of mitosis and is tightly regulated. CDK1-cyclin B is a serine/threonine protein kinase composed of the catalytic subunit CDK1 and its positive regulatory subunit cyclin B (B1 isoform). Binding of CDK1 to cyclin B is essential for activation of the kinase. Phosphorylation of T161 is required for activation of the CDK1-cyclin B complex and is mediated by the CDK activating kinase (CAK). During G2 phase, CDK1-cyclin B complex is held in an inactive state by phosphorylation of CDK1 at the two negative regulatory sites, T14 and Y15 by CDK1 inhibitory protein kinases, Myt1 and Wee1 respectively. Dephosphorylation of T14 and Y15 by cell division cycle (CDC25) protein phosphatase in late G2 phase activates the CDK1-cyclin B complex and triggers the initiation of mitosis. During expression in insect cells, the recombiniant CDK1-cyclin B is activatedin vivoby endogenous kinase (1–4).
Highlights
Protein serine/threonine kinase
Human, recombinant (S. frugiperda S19)
Product Source
Isolated fromSpodoptera frugiperda(Sf9) cells infected with recombinant baculovirus carrying human CDK1 and human cyclin B (1,2) (kindly provided by Dr. H. Piwnica-Worms).
Recognition Determinant
The substrate specificity of CDK1-cyclin B shows an absolute requirement for Pro in the +1 position, a secondary requirement for Arg or Lys at +3, and a preference for basic residues at +2 or +3 positions. The recognition motif for phosphorylation by CDK1-cyclin B isS/TPXR/K, frequently with additional basic residues on either side (K/RSPR/PR/K/H) (5).