title: Cyclin B and cyclin A confer different substrate recognition properties on CDK2.
abstract: The transitions of the cell cycle are regulated by the cyclin dependent protein kinases (CDKs). The cyclins activate their respective CDKs and confer substrate recognition properties. We report the structure of phospho-CDK2/cyclin B and show that cyclin B confers M phase-like properties on CDK2, the kinase that is usually associated with S phase. Cyclin B produces an almost identical activated conformation of CDK2 as that produced by cyclin A. There are differences between cyclin A and cyclin B at the recruitment site, which in cyclin A is used to recruit substrates containing an RXL motif. Because of sequence differences this site in cyclin B binds RXL motifs more weakly than in cyclin A. Despite similarity in kinase structures, phospho-CDK2/cyclin B phosphorylates substrates, such as nuclear lamin and a model peptide derived from p107, at sequences SPXX that differ from the canonical CDK2/cyclin A substrate recognition motif, SPXK. CDK2/cyclin B phosphorylation at these non-canonical sites is not dependent on the presence of a RXL recruitment motif. The p107 peptide contains two SP motifs each followed by a non-canonical sequence of which only one site (Ser640) is phosphorylated by pCDK2/cyclin A while two sites are phosphorylated by pCDK2/cyclin B. The second site is too close to the RXL motif to allow the cyclin A recruitment site to be effective, as previous work has shown that there must be at least 16 residues between the catalytic site serine and the RXL motif. Thus the cyclins A and B in addition to their role in promoting the activatory conformational switch in CDK2, also provide differential substrate specificity.
authors.affiliation: Laboratory of Molecular Biophysics, Department of Biochemistry, University of Oxford, Oxford, UK.
authors.forename: Nick R
authors.initials: NR
authors.lastname: Brown
authors.forename: Ed D
authors.initials: ED
authors.lastname: Lowe
authors.forename: Ed
authors.initials: E
authors.lastname: Petri
authors.forename: Vicky
authors.initials: V
authors.lastname: Skamnaki
authors.forename: Robin
authors.initials: R
authors.lastname: Antrobus
authors.forename: Louise N
authors.initials: LN
authors.lastname: Johnson
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D020134:Catalytic Domain; D002455:Cell Division; D018360:Crystallography, X-Ray; D019925:Cyclin A / Q000737:chemistry* / Q000378:metabolism; D056751:Cyclin A2; D019926:Cyclin B / Q000737:chemistry* / Q000378:metabolism; D056744:Cyclin B1; D051357:Cyclin-Dependent Kinase 2 / Q000737:chemistry* / Q000378:metabolism; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000737:chemistry / Q000378:metabolism; D004789:Enzyme Activation; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D034882:Lamins / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000378:metabolism; D010766:Phosphorylation; D011485:Protein Binding; D011487:Protein Conformation; D025941:Protein Interaction Mapping; D011499:Protein Processing, Post-Translational; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D050720:Retinoblastoma-Like Protein p107 / Q000737:chemistry / Q000378:metabolism; D016196:S Phase; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D021241:Spectrometry, Mass, Electrospray Ionization; D013329:Structure-Activity Relationship; D013379:Substrate Specificity; D020349:Surface Plasmon Resonance; D053719:Tandem Mass Spectrometry
chemical_list: C503721:CCNA2 protein, human; C534699:CCNB1 protein, human; D019925:Cyclin A; D056751:Cyclin A2; D019926:Cyclin B; D056744:Cyclin B1; D034882:Lamins; D010446:Peptide Fragments; C493844:RBL1 protein, human; D011993:Recombinant Fusion Proteins; D050720:Retinoblastoma-Like Protein p107; D050760:Cyclin-Dependent Kinase Inhibitor p27; C495894:CDK2 protein, human; D051357:Cyclin-Dependent Kinase 2