title: Molecular characterization of Ypi1, a novel Saccharomyces cerevisiae type 1 protein phosphatase inhibitor.
abstract: The Saccharomyces cerevisiae open reading frame YFR003c encodes a small (155-amino acid) hydrophilic protein that we identified as a novel, heat-stable inhibitor of type 1 protein phosphatase (Ypi1). Ypi1 interacts physically in vitro with both Glc7 and Ppz1 phosphatase catalytic subunits, as shown by pull-down assays. Ypi1 inhibits Glc7 but appears to be less effective toward Ppz1 phosphatase activity under the conditions tested. Ypi1 contains a 48RHNVRW53 sequence, which resembles the characteristic consensus PP1 phosphatase binding motif. A W53A mutation within this motif abolishes both binding to and inhibition of Glc7 and Ppz1 phosphatases. Deletion of YPI1 is lethal, suggesting a relevant role of the inhibitor in yeast physiology. Cells overexpressing Ypi1 display a number of phenotypes consistent with an inhibitory role of this protein on Glc7, such as decreased glycogen content and an increased growth defect in a slt2/mpk1 mitogen-activated protein kinase-deficient background. Taking together, these results define Ypi1 as the first inhibitory subunit of Glc7 identified in budding yeast.
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D020134:Catalytic Domain; D004305:Dose-Response Relationship, Drug; D004926:Escherichia coli / Q000378:metabolism; D017353:Gene Deletion; D005982:Glutathione Transferase / Q000378:metabolism; D006003:Glycogen / Q000737:chemistry; D015151:Immunoblotting; D047908:Intracellular Signaling Peptides and Proteins; D020928:Mitogen-Activated Protein Kinases; D008969:Molecular Sequence Data; D009154:Mutation; D009841:Oligonucleotides / Q000737:chemistry; D010641:Phenotype; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors* / Q000737:chemistry; D010766:Phosphorylation; D010802:Phylogeny; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D054645:Protein Phosphatase 1; D011994:Recombinant Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000235:genetics*; D013696:Temperature; D013997:Time Factors
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; D009841:Oligonucleotides; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; C480163:Ypi1 protein, S cerevisiae; D006003:Glycogen; D005982:Glutathione Transferase; D020928:Mitogen-Activated Protein Kinases; C072724:SLT2 protein, S cerevisiae; C092048:GLC7 protein, S cerevisiae; C075119:PPZ1 protein, S cerevisiae; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1