Molecular characterization of Ypi1, a novel Saccharomyces cerevisiae type 1 protein phosphatase inhibitor.

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:
Amino Acid Motifs, Amino Acid Sequence, Catalytic Domain, Dose-Response Relationship, Drug, Escherichia coli, Gene Deletion, Glutathione Transferase, Glycogen, Immunoblotting, Intracellular Signaling Peptides and Proteins, Mitogen-Activated Protein Kinases, Molecular Sequence Data, Mutation, Oligonucleotides, Phenotype, Phosphoprotein Phosphatases, Phosphorylation, Phylogeny, Plasmids, Protein Binding, Protein Phosphatase 1, Recombinant Proteins, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins, Temperature, Time Factors
J. Biol. Chem.
Date: Nov. 28, 2003
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