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  • Title: A novel and essential mechanism determining specificity and activity of protein phosphatase 2A (PP2A) in vivo.
    Author: Fellner T, Lackner DH, Hombauer H, Piribauer P, Mudrak I, Zaragoza K, Juno C, Ogris E.
    Journal: Genes Dev; 2003 Sep 01; 17(17):2138-50. PubMed ID: 12952889.
    Abstract:
    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.
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