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A novel and essential mechanism determining specificity and activity of protein phosphatase 2A (PP2A) in vivo.

Protein phosphatase 2A (PP2A) is an essential intracellular serine/threonine phosphatase containing a catalytic subunit that possesses the potential to dephosphorylate promiscuously tyrosine-phosphorylated substrates in vitro. How PP2A acquires its intracellular specificity and activity for serine/threonine-phosphorylated substrates is unknown. Here we report a novel and phylogenetically conserved mechanism to generate active phospho-serine/threonine-specific PP2A in vivo. Phosphotyrosyl phosphatase activator (PTPA), a protein of so far unknown intracellular function, is required for the biogenesis of active and specific PP2A. Deletion of the yeast PTPA homologs generated a PP2A catalytic subunit with a conformation different from the wild-type enzyme, as indicated by its altered substrate specificity, reduced protein stability, and metal dependence. Complementation and RNA-interference experiments showed that PTPA fulfills an essential function conserved from yeast to man.

Pubmed ID: 12952889


  • Fellner T
  • Lackner DH
  • Hombauer H
  • Piribauer P
  • Mudrak I
  • Zaragoza K
  • Juno C
  • Ogris E


Genes & development

Publication Data

September 1, 2003

Associated Grants


Mesh Terms

  • 3T3 Cells
  • Animals
  • Apoptosis
  • Binding Sites
  • HeLa Cells
  • Humans
  • Metals
  • Mice
  • Mutation
  • Phosphoprotein Phosphatases
  • Protein Phosphatase 2
  • RNA Interference
  • Substrate Specificity