Crystal structure of the p27Kip1 cyclin-dependent-kinase inibitor bound to the cyclin A-Cdk2 complex

The crystal structure of the human p27^Kip1 kinase inhibitory domain bound to the phosphorylated cyclin A-cyclin-dependent kinase 2 (Cdk2) complex has been determined at 2.3 Å. p27^Kip1 binds the complex as an extended structure interacting with both cyclin A and Cdk2. On cyclin A, it binds in a groove formed by conserved cyclin box residues. On Cdk2, it binds and rearranges the amino-terminal lobe and also inserts into the catalytic cleft, mimicking ATP.