The cdc2-related protein p40MO15 is the catalytic subunit of a protein kinase that can activate p33cdk2 and p34cdc2.
Activation of the cyclin-dependent protein kinases p34cdc2 and p33cdk2 requires binding with a cyclin partner and phosphorylation on the first threonine residue in the sequence THEVVTLWYRAPE. We present evidence that this threonine residue, number 160 in p33cdk2, can be specifically phosphorylated by a cdc2-related protein kinase from Xenopus oocytes called p40MO15. Binding to cyclin A and phosphorylation of this threonine are both required to activate fully the histone H1 kinase activity of p33cdk2. In cell extracts, a portion of p40MO15 is found in a high molecular weight complex that is considerably more active than a lower molecular weight form. Wild-type MO15 protein expressed in bacteria does not possess kinase activity, but acquires p33cdk2-T160 kinase activity after incubation with cell extract and ATP. We conclude that p40MO15 corresponds to CAK (cdc2/cdk2 activating kinase) and speculate that, like p33cdk2 and p34cdc2, p40MO15 requires activation by phosphorylation and association with a companion subunit.
Imperial Cancer Research Fund, Clare Hall Laboratories, Potters Bar, Herts, UK.
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Poon
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Yamashita
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Adamczewski
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Hunt
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Shuttleworth
D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D016203:CDC2 Protein Kinase / Q000378:metabolism*; D042846:CDC2-CDC28 Kinases; D002384:Catalysis; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases; D016213:Cyclins / Q000502:physiology; D004789:Enzyme Activation; D004926:Escherichia coli; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides; D010766:Phosphorylation; D011233:Precipitin Tests; D006656:Protamine Kinase / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D013379:Substrate Specificity; D013912:Threonine / Q000378:metabolism; D014981:Xenopus; D029867:Xenopus Proteins; D000095043:Cyclin-Dependent Kinase-Activating Kinase
D016213:Cyclins; D009838:Oligodeoxyribonucleotides; D011506:Proteins; D011994:Recombinant Proteins; D029867:Xenopus Proteins; D013912:Threonine; D000255:Adenosine Triphosphate; D011494:Protein Kinases; D006656:Protamine Kinase; D017346:Protein Serine-Threonine Kinases; D016203:CDC2 Protein Kinase; D042846:CDC2-CDC28 Kinases; C495891:Cdk2 protein, Xenopus; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases; D000095043:Cyclin-Dependent Kinase-Activating Kinase