title: Purification and molecular cloning of Plx1, a Cdc25-regulatory kinase from Xenopus egg extracts.
abstract: Cdc2, the cyclin-dependent kinase that controls mitosis, is negatively regulated by phosphorylation on its threonine-14 and tyrosine-15 residues. Cdc25, the phosphatase that dephosphorylates both of these residues, undergoes activation and phosphorylation by multiple kinases at mitosis. Plx1, a kinase that associates with and phosphorylates the amino-terminal domain of Cdc25, was purified extensively from Xenopus egg extracts. Cloning of its complementary DNA revealed that Plx1 is related to the Polo family of protein kinases. Recombinant Plx1 phosphorylated Cdc25 and stimulated its activity in a purified system. Cdc25 phosphorylated by Plx1 reacted strongly with MPM-2, a monoclonal antibody to mitotic phosphoproteins. These studies indicate that Plx1 may participate in control of mitotic progression.
authors.affiliation: Division of Biology, 216-76, Howard Hughes Medical Institute, California Institute of Technology, Pasadena, CA 91125, USA.
authors.forename: A
authors.initials: A
authors.lastname: Kumagai
authors.forename: W G
authors.initials: WG
authors.lastname: Dunphy
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D016203:CDC2 Protein Kinase / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000378:metabolism*; D003001:Cloning, Molecular; D016213:Cyclins / Q000378:metabolism; D004789:Enzyme Activation; D008969:Molecular Sequence Data; D009154:Mutation; D009865:Oocytes / Q000201:enzymology; D010449:Peptide Mapping; D010749:Phosphoprotein Phosphatases / Q000737:chemistry / Q000378:metabolism*; D010766:Phosphorylation; D010768:Phosphoserine / Q000032:analysis; D010769:Phosphothreonine / Q000032:analysis; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D014981:Xenopus; D029867:Xenopus Proteins; D020687:cdc25 Phosphatases; D000097869:Polo-Like Kinase 1
chemical_list: D016203:CDC2 Protein Kinase; D018797:Cell Cycle Proteins; D016213:Cyclins; D010749:Phosphoprotein Phosphatases; D010768:Phosphoserine; D010769:Phosphothreonine; D017346:Protein Serine-Threonine Kinases; D011994:Recombinant Proteins; D029867:Xenopus Proteins; D020687:cdc25 Phosphatases; C101085:Plk1 protein, Xenopus; D000097869:Polo-Like Kinase 1