InterPro domain: IPR036858

In eukaryotes, cyclin-dependent protein kinases interact with cyclins to regulate cell cycleprogression, and are required for the G1 and G2 stages of cell division [ 1 ]. Theproteins bind to a regulatory subunit, cyclin-dependent kinase regulatory subunit (CKS),which is essential for their function. This regulatory subunit is a small protein of 79 to 150residues. In yeast (gene CKS1) and in fission yeast (gene suc1) a single isoform is known,while mammals have two highly related isoforms. The regulatory subunits exist as hexamers,formed by the symmetrical assembly of 3 interlocked homodimers, creating an unusual 12-stranded beta-barrel structure [ 2 ]. Through the barrel centre runs a 12A diametertunnel, lined by 6 exposed helix pairs [ 3 ]. Six kinase units can be modelled to bind thehexameric structure, which may thus act as a hub for cyclin-dependent protein kinasemultimerisation [ 4 , 4 ].

1. p13suc1 acts in the fission yeast cell division cycle as a component of the p34cdc2 protein kinase. EMBO J. 6, 3507-14
2. Human CksHs2 atomic structure: a role for its hexameric assembly in cell cycle control. Science 262, 387-95
3. The Cdk-associated protein Cks1 functions both in G1 and G2 in Saccharomyces cerevisiae. Genes Dev. 7, 822-32