title: The chaperone-like properties of mammalian inhibitor-2 are conserved in a Drosophila homologue.
abstract: Phosphatase inhibitor-2 (I-2) is a mammalian phosphoprotein that binds to the catalytic subunit of type 1 serine/threonine phosphoprotein phosphatase (PP1c) and inhibits its activity in vitro. Recombinant PP1c differs from native PP1c in several biochemical criteria, including the requirement for Mn(2+), sensitivity to vanadate, and p-nitrophenyl phosphate (pNPP) phosphatase activity. I-2 can convert recombinant PP1c into a native-like activity in vitro. It has therefore been suggested that I-2 may act as a molecular chaperone for PP1 in vivo. We have identified a Drosophila homologue (I-2Dm) in a two-hybrid screen for PP1c-binding proteins. The sequence of I-2Dm is 35% identical with that of I-2, whereas the catalytic subunits themselves are >85% identical in flies and humans; however, we show that many biochemical properties of I-2 are conserved. Like I-2, I-2Dm can convert recombinant PP1c to a native-like activity. This strongly suggests that this ability is an essential, conserved role of I-2 and I-2Dm.
authors.affiliation: Department of Zoology, University of Oxford, U.K.
authors.forename: D
authors.initials: D
authors.lastname: Bennett
authors.forename: B
authors.initials: B
authors.lastname: Szöor
authors.forename: L
authors.initials: L
authors.lastname: Alphey
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002384:Catalysis / Q000187:drug effects; D017124:Conserved Sequence; D018076:DNA, Complementary / Q000302:isolation & purification; D004331:Drosophila melanogaster / Q000737:chemistry* / Q000235:genetics; D004789:Enzyme Activation / Q000187:drug effects / Q000235:genetics; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000494:pharmacology; D006358:Hot Temperature; D006801:Humans; D019476:Insect Proteins / Q000096:biosynthesis / Q000737:chemistry* / Q000235:genetics / Q000494:pharmacology; D018832:Molecular Chaperones / Q000737:chemistry*; D008969:Molecular Sequence Data; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D014176:Protein Biosynthesis; D054645:Protein Phosphatase 1; D011506:Proteins / Q000737:chemistry* / Q000235:genetics / Q000494:pharmacology; D011817:Rabbits; D051381:Rats; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology; D017421:Sequence Analysis; D017386:Sequence Homology, Amino Acid; D000097847:Protein Phosphatase Inhibitory Proteins
chemical_list: D018076:DNA, Complementary; D004791:Enzyme Inhibitors; D019476:Insect Proteins; D018832:Molecular Chaperones; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; D011506:Proteins; D011994:Recombinant Proteins; C024833:protein phosphatase inhibitor-2; D000097847:Protein Phosphatase Inhibitory Proteins