title: Cdc2 protein kinase is complexed with both cyclin A and B: evidence for proteolytic inactivation of MPF.
abstract: In the clam, Spisula, two previously described proteins known as cyclin A and B display the unusual property of selective proteolytic degradation at the end of each mitosis. We show here that clam oocytes and embryos contain a cdc2 protein kinase. This protein kinase is a component of the M phase promoting factor (MPF) in frog eggs and the M phase-specific histone H1 kinase in starfish. Clam cdc2 is found in association with both cyclin A and B, probably not as a trimolecular association, but as separate cdc2/cyclin A and cdc2/cyclin B complexes. Clam cdc2 and the associated cyclins bind to p13suc1-Sepharose. The p13-bound complex, and also anti-cyclin A or B immunoprecipitates, each display cell cycle-dependent histone H1 kinase activity. We suggest that in addition to the cdc2 protein kinase, the cyclins are further components of the M phase promoting factor and that cyclin proteolysis provides the mechanism of MPF inactivation and thus exit from mitosis.
authors.affiliation: Cold Spring Harbor Laboratory, New York 11724.
authors.forename: G
authors.initials: G
authors.lastname: Draetta
authors.forename: F
authors.initials: F
authors.lastname: Luca
authors.forename: J
authors.initials: J
authors.lastname: Westendorf
authors.forename: L
authors.initials: L
authors.lastname: Brizuela
authors.forename: J
authors.initials: J
authors.lastname: Ruderman
authors.forename: D
authors.initials: D
authors.lastname: Beach
mesh_terms: D000818:Animals; D049872:Bivalvia / Q000502:physiology*; D016203:CDC2 Protein Kinase; D016213:Cyclins; D006133:Growth Substances / Q000502:physiology*; D007447:Invertebrate Hormones / Q000502:physiology*; D016200:Maturation-Promoting Factor; D008540:Meiosis; D008938:Mitosis; D008970:Molecular Weight; D009865:Oocytes / Q000502:physiology; D010750:Phosphoproteins / Q000502:physiology*; D006656:Protamine Kinase / Q000378:metabolism; D011494:Protein Kinases / Q000502:physiology*
chemical_list: D016213:Cyclins; D006133:Growth Substances; D007447:Invertebrate Hormones; D010750:Phosphoproteins; D011494:Protein Kinases; D006656:Protamine Kinase; D016203:CDC2 Protein Kinase; D016200:Maturation-Promoting Factor