Journal of Biological Chemistry
Enzyme Catalysis and RegulationSelection of Protein Phosphatase 2A Regulatory Subunits Is Mediated by the C Terminus of the Catalytic Subunit*
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Note Added in Proof—When this work was finished and submitted for review, we became aware of the work by E. Sontag and co-workers (42). The authors basically came to the same conclusions that C-terminal methylation of PP2AC and phosphorylation of Tyr307 and Thr304 are differentially important for formation of the different holoenzyme forms. There are some apparent discrepancies, though, that might be explained by the different experimental approaches. Whereas in our study the pulldowns of the individual GST fusions with the “third” subunits would reveal rather the intrinsic affinity of a specific subunit for the mutant forms of PP2AC, the use of an IP approach with the mutant catalytic subunits would largely reflect the presence of the relative amounts and affinities of the different subunits in the cellular conditions used. As discussed, we cannot explain the conflicting data of the methylation deficiency of Y307F in our work and in Ref. 4 as opposed to the results in Ref. 3 and 19, and now also 42, which might originate from the use of one and the same construct in the latter studies.
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This work was supported by grants from the “Geconcerteerde Onderzoeks-Acties” (Flemish government), IUAP “Interuniversity Attraction Poles” (Belgian Science Policy), and F.W.O.-Vlaanderen. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.