title: Critical role for the 310 helix region of p57(Kip2) in cyclin-dependent kinase 2 inhibition and growth suppression.
abstract: Although crystal structural analysis of cyclin A/cyclin-dependent kinase 2 (Cdk2)/p27 (Russo, A. A., Jeffrey, P. D., Pattern, A. K., Massague, J., and Pavletich, N. P. (1996) Nature 382, 325-331) has suggested that the 310 helix region in Cdk inhibitors of the Cip/Kip family may be involved in the inhibition of cyclin/Cdk activities, there is no biochemical evidence supporting this hypothesis. In the present study, we demonstrated that cyclin and Cdk binding domains of p57 were necessary but were not sufficient in themselves for the inhibition of cyclin A/Cdk2 and cyclin E/Cdk2, and that the 3(10) helix region of this protein is indispensable for the inhibition of these complexes. In contrast, the 3(10) helix regions of p21 and p27 were not required, and cyclin- and Cdk-binding domains alone were sufficient for the inhibition of all cyclin/Cdk complexes examined. Site-directed mutagenesis identified phenylalanine 79 and tyrosine 80 within the 3(10) helix region of p57 as crucial residues for kinase inhibition, supporting the structural evidence that the 3(10) helix binds deep inside the catalytic cleft of Cdk2, mimicking ATP. Mutations within the 3(10) helix region of the p57 molecule completely abolished the ability to arrest the cell cycle at G1 in vivo. These results indicate that this region is specifically utilized by p57 in selectively inhibiting cyclin A or E/Cdk2+ activities. Thus the 3(10) helix motif may confer a specific regulatory mechanism by which p57 differentially regulates Cdk2 and Cdk4 activities.
authors.affiliation: Department of Geriatric Research, National Institute for Longevity Sciences, Morioka, Obu, Aichi 474, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Hashimoto
authors.forename: K
authors.initials: K
authors.lastname: Kohri
authors.forename: Y
authors.initials: Y
authors.lastname: Kaneko
authors.forename: H
authors.initials: H
authors.lastname: Morisaki
authors.forename: T
authors.initials: T
authors.lastname: Kato
authors.forename: K
authors.initials: K
authors.lastname: Ikeda
authors.forename: M
authors.initials: M
authors.lastname: Nakanishi
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D016367:Baculoviridae; D001665:Binding Sites; D042846:CDC2-CDC28 Kinases; D018360:Crystallography, X-Ray; D019925:Cyclin A / Q000037:antagonists & inhibitors; D019927:Cyclin E / Q000037:antagonists & inhibitors; D051357:Cyclin-Dependent Kinase 2; D050761:Cyclin-Dependent Kinase Inhibitor p57; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors*; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000378:metabolism*; D004926:Escherichia coli; D006131:Growth Inhibitors / Q000378:metabolism*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009687:Nuclear Proteins / Q000737:chemistry / Q000378:metabolism*; D011487:Protein Conformation; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors*; D017433:Protein Structure, Secondary; D016415:Sequence Alignment; D018411:Spodoptera; D013329:Structure-Activity Relationship
chemical_list: D019925:Cyclin A; D019927:Cyclin E; D050761:Cyclin-Dependent Kinase Inhibitor p57; D004791:Enzyme Inhibitors; D006131:Growth Inhibitors; D009687:Nuclear Proteins; D000255:Adenosine Triphosphate; D017346:Protein Serine-Threonine Kinases; D042846:CDC2-CDC28 Kinases; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases