The B' γ subunit of protein phosphatase 2A is phosphorylated by cGMP-dependent protein kinase

P. Komalavilas, A. A. DePaoli-Roach, T. M. Lincoln

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Nitric oxide regulates vascular tone by elevating smooth muscle cell cGMP levels. Activation of cGMP-dependent protein kinase (PKG) results in the lowering of intracellular Ca2+ levels producing relaxation. Previous studies have shown that PKG stimulates the calcium- activated K+ channel by dephosphorylation. To further understand the mechanism of the effects of PKG on cell function, we examined the phosphorylation of the B' γ subunit of protein phosphatase 2A (PP2A) by PKG The B' γ subunit was expressed in E.coli and purified on a Ni-NTA resin column. The eluted protein was phosphorylated using PKG and the catalytic subunit of cAMP-dependent protein kinase (PKA) in vitro. The results demonstrated that the B' γ subunit is phosphorylated in a time-dependent fashion by both PKG and PKA upto a stoichiometry of 1.8 mol of phosphate/mol of the protein. Using comparable amounts of PKG and PKA kinase activity, PKG catalyzed maximal phosphorylation within 2 min, whereas PKA catalyzed maximal phosphorylation in 10 min. These results suggest that the regulation of PP2A activity may occur through the phosphorylation of the B' γ subunit.

Original languageEnglish (US)
Pages (from-to)A326
JournalFASEB Journal
Issue number3
StatePublished - Dec 1 1997


ASJC Scopus subject areas

  • Biotechnology
  • Biochemistry
  • Molecular Biology
  • Genetics

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