title: Three-dimensional structure of human cyclin H, a positive regulator of the CDK-activating kinase.
abstract: Cyclin-dependent kinases (CDKs), which play a key role in cell cycle control, are activated by the CDK activating kinase (CAK), which activates cyclin-bound CDKs by phosphorylation at a specific threonine residue. Vertebrate CAK contains two key components: a kinase subunit with homology to its substrate CDKs and a regulatory subunit with homology to cyclins. We have determined the X-ray crystal structure of the regulatory subunit of CAK, cyclin H, at 2.6 A resolution. Cyclin H contains two alpha-helical core domains with a fold similar to that of cyclin A, a regulatory subunit of CAK substrate CDK2, and of TFIIB, a transcription factor. Outside of the core domains, the N- and C-terminal regions of the three structures are completely different. The conformational differences between cyclin H and A structures may reflect functional differences between the two cyclins.
authors.affiliation: Department of Chemistry, University of California, Berkeley 94720, USA.
authors.forename: K K
authors.initials: KK
authors.lastname: Kim
authors.forename: H M
authors.initials: HM
authors.lastname: Chamberlin
authors.forename: D O
authors.initials: DO
authors.lastname: Morgan
authors.forename: S H
authors.initials: SH
authors.lastname: Kim
mesh_terms: D000595:Amino Acid Sequence; D003001:Cloning, Molecular; D056748:Cyclin H; D018844:Cyclin-Dependent Kinases; D016213:Cyclins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008969:Molecular Sequence Data; D017510:Protein Folding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D016415:Sequence Alignment; D017421:Sequence Analysis; D000095043:Cyclin-Dependent Kinase-Activating Kinase
chemical_list: C534751:CCNH protein, human; D056748:Cyclin H; D016213:Cyclins; D017346:Protein Serine-Threonine Kinases; D018844:Cyclin-Dependent Kinases; D000095043:Cyclin-Dependent Kinase-Activating Kinase