title: Role of intrinsic flexibility in signal transduction mediated by the cell cycle regulator, p27 Kip1.
abstract: p27(Kip1) (p27), which controls eukaryotic cell division through interactions with cyclin-dependent kinases (Cdks), integrates and transduces promitogenic signals from various nonreceptor tyrosine kinases by orchestrating its own phosphorylation, ubiquitination and degradation. Intrinsic flexibility allows p27 to act as a "conduit" for sequential signaling mediated by tyrosine and threonine phosphorylation and ubiquitination. While the structural features of the Cdk/cyclin-binding domain of p27 are understood, how the C-terminal regulatory domain coordinates multistep signaling leading to p27 degradation is poorly understood. We show that the 100-residue p27 C-terminal domain is extended and flexible when p27 is bound to Cdk2/cyclin A. We propose that the intrinsic flexibility of p27 provides a molecular basis for the sequential signal transduction conduit that regulates p27 degradation and cell division. Other intrinsically unstructured proteins possessing multiple sites of posttranslational modification may participate in similar signaling conduits.
authors.affiliation: Department of Structural Biology, St. Jude Children's Research Hospital, 332 North Lauderdale St., Memphis, TN 38105, USA.
authors.forename: Charles A
authors.initials: CA
authors.lastname: Galea
authors.forename: Amanda
authors.initials: A
authors.lastname: Nourse
authors.forename: Yuefeng
authors.initials: Y
authors.lastname: Wang
authors.forename: Sivashankar G
authors.initials: SG
authors.lastname: Sivakolundu
authors.forename: William T
authors.initials: WT
authors.lastname: Heller
authors.forename: Richard W
authors.initials: RW
authors.lastname: Kriwacki
mesh_terms: D019925:Cyclin A / Q000378:metabolism; D051357:Cyclin-Dependent Kinase 2 / Q000378:metabolism; D050760:Cyclin-Dependent Kinase Inhibitor p27; D047908:Intracellular Signaling Peptides and Proteins / Q000737:chemistry* / Q000378:metabolism*; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D010766:Phosphorylation; D015398:Signal Transduction
chemical_list: C436291:CDKN1B protein, human; D019925:Cyclin A; D047908:Intracellular Signaling Peptides and Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; C495894:CDK2 protein, human; D051357:Cyclin-Dependent Kinase 2