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Dephosphorylation of human cyclin-dependent kinases by protein phosphatase type 2C alpha and beta 2 isoforms.

We previously reported that the activating phosphorylation on cyclin-dependent kinases in yeast (Cdc28p) and in humans (Cdk2) is removed by type 2C protein phosphatases. In this study, we characterize this PP2C-like activity in HeLa cell extract and determine that it is due to PP2C beta 2, a novel PP2C beta isoform, and to PP2C alpha. PP2C alpha and PP2C beta 2 co-purified with Mg(2+)-dependent Cdk2/Cdk6 phosphatase activity in DEAE-Sepharose, Superdex-200, and Mono Q chromatographies. Moreover, purified recombinant PP2C alpha and PP2C beta 2 proteins efficiently dephosphorylated monomeric Cdk2/Cdk6 in vitro. The dephosphorylation of Cdk2 and Cdk6 by PP2C isoforms was inhibited by the binding of cyclins. We found that the PP2C-like activity in HeLa cell extract, partially purified HeLa PP2C alpha and PP2C beta 2 isoforms, and the recombinant PP2Cs exhibited a comparable substrate preference for a phosphothreonine containing substrate, consistent with the conservation of threonine residues at the site of activating phosphorylation in CDKs.

Pubmed ID: 10934208 RIS Download

Mesh terms: Amino Acid Sequence | Animals | Chromatography, Ion Exchange | Cyclin-Dependent Kinases | Cyclins | HeLa Cells | Humans | Isoenzymes | Mice | Molecular Sequence Data | Phosphoprotein Phosphatases | Phosphorylation | Protein Phosphatase 2 | Protein Phosphatase 2C | Rats | Saccharomyces cerevisiae Proteins | Sequence Homology, Amino Acid | Substrate Specificity

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Associated grants

  • Agency: NIGMS NIH HHS, Id: GM47830

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