title: Specificity determinants of recruitment peptides bound to phospho-CDK2/cyclin A.
abstract: 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.
authors.affiliation: Laboratory of Molecular Biophysics, University of Oxford, Rex Richards Building, Oxford OX1 3QU, UK.
authors.forename: Edward D
authors.initials: ED
authors.lastname: Lowe
authors.forename: Ivo
authors.initials: I
authors.lastname: Tews
authors.forename: Kin Yip
authors.initials: KY
authors.lastname: Cheng
authors.forename: Nick R
authors.initials: NR
authors.lastname: Brown
authors.forename: Sheraz
authors.initials: S
authors.lastname: Gul
authors.forename: Martin E M
authors.initials: ME
authors.lastname: Noble
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Gamblin
authors.forename: Louise N
authors.initials: LN
authors.lastname: Johnson
mesh_terms: D020816:Amino Acid Motifs; D042846:CDC2-CDC28 Kinases; D002151:Calorimetry; D018797:Cell Cycle Proteins / Q000737:chemistry; D018360:Crystallography, X-Ray; D019925:Cyclin A / Q000737:chemistry*; D051357:Cyclin-Dependent Kinase 2; D050760:Cyclin-Dependent Kinase Inhibitor p27; D018844:Cyclin-Dependent Kinases / Q000737:chemistry*; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D006801:Humans; D046911:Macromolecular Substances; D008958:Models, Molecular; D010446:Peptide Fragments / Q000737:chemistry*; D010766:Phosphorylation; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry*; D016160:Retinoblastoma Protein / Q000737:chemistry; D013379:Substrate Specificity; D014157:Transcription Factors / Q000737:chemistry*; D016159:Tumor Suppressor Protein p53 / Q000737:chemistry; D025521:Tumor Suppressor Proteins / Q000737:chemistry
chemical_list: D018797:Cell Cycle Proteins; D019925:Cyclin A; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; C493753:E2F1 protein, human; D046911:Macromolecular Substances; D010446:Peptide Fragments; D016160:Retinoblastoma Protein; D014157:Transcription Factors; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; D017346:Protein Serine-Threonine Kinases; D042846:CDC2-CDC28 Kinases; C495894:CDK2 protein, human; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases