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.
SciCrunch is a data sharing and display platform. Anyone can create a custom portal where they can select searchable subsets of hundreds of data sources, brand their web pages and create their community. SciCrunch will push data updates automatically to all portals on a weekly basis. User communities can also add their own data to scicrunch, however this is not currently a free service.