PDB 1H26 deposited: 2002-07-31 modified: 2009-02-24
Authors Brown, N.R., Cheng, K.Y., Gamblin, S., Gul, S., Johnson, L.N., Lowe, E.D., Noble, M.E.M., Tews, I.
Structure factors resolution 2.24 rfactor 0.216 rfree 0.268
DPI 0.62 theoretical min: 0.29
Related PDB Entries 1GY3 1H24 1H25 1H27 1H28 1QMZ

"Progression through S phase of the eukaryotic cell cycle is regulated by the action of the cyclin dependent protein kinase 2 (CDK2) in association with cyclin A. CDK2/cyclin A phosphorylates numerous substrates. Substrate specificity often employs a dual recognition strategy in which the sequence flanking the phospho-acceptor site (Ser.Pro.X.Arg/Lys) is recognized by CDK2, while the cyclin A component of the complex contains a hydrophobic site that binds Arg/Lys.X.Leu (""RXL"" or ""KXL"") substrate recruitment motifs. To determine additional sequence specificity motifs around the RXL sequence, we have performed X-ray crystallographic studies at 2.3 A resolution and isothermal calorimetry measurements on complexes of phospho-CDK2/cyclin A with a recruitment peptide derived from E2F1 and with shorter 11-mer peptides from p53, pRb, p27, E2F1, and p107. The results show that the cyclin recruitment site accommodates a second hydrophobic residue either immediately C-terminal or next adjacent to the leucine of the ""RXL"" motif and that this site makes important contributions to the recruitment peptide recognition. The arginine of the RXL motif contacts a glutamate, Glu220, on the cyclin. In those substrates that contain a KXL motif, no ionic interactions are observed with the lysine. The sequences N-terminal to the ""RXL"" motif of the individual peptides show no conservation, but nevertheless make common contacts to the cyclin through main chain interactions. Thus, the recruitment site is able to recognize diverse but conformationally constrained target sequences. The observations have implications for the further identification of physiological substrates of CDK2/cyclin A and the design of specific inhibitors."

Biochemistry 2002 Dec; 41(52):15625- doi:10.1021/BI0268910

Progression through the eukaryotic cell cycle is driven by the orderly activation of cyclin-dependent kinases (CDKs). For activity, CDKs require association with a cyclin and phosphorylation by a separate protein kinase at a conserved threonine residue (T160 in CDK2). Here we present the structure of a complex consisting of phosphorylated CDK2 and cyclin A together with an optimal peptide substrate, HHASPRK. This structure provides an explanation for the specificity of CDK2 towards the proline that follows the phosphorylatable serine of the substrate peptide, and the requirement for the basic residue in the P+3 position of the substrate. We also present the structure of phosphorylated CDK2 plus cyclin A3 in complex with residues 658-668 from the CDK2 substrate p107. These residues include the RXL motif required to target p107 to cyclins. This structure explains the specificity of the RXL motif for cyclins.

Nat.Cell Biol. 1999 Nov; 1(7):438- doi:10.1038/15674

Cross References
Database source Identifier Description
PubMed 12501191 BICHAW
PubMed 10559988
Biomolecule Structure Assembly Serial Assembly Type Conformational State Chains Ligands Atoms
1H26/1 1H26 1 trimer 0 3 0 4120
1H26/2 1H26 2 dimer 0 2 0 3727