Glycosylphosphatidylinositols (GPIs) are found in all eukaryotes and are synthesized in a pathway that starts with the transfer of N-acetylglucosamine (GlcNAc) from UDP-GlcNAc to phosphatidylinositol (PI). This reaction is carried out by a protein complex, three of whose subunits in humans, hGpi1p, Pig-Cp and Pig-Ap, have sequence and functional homologues in the Saccharomyces cerevisiae Gpi1, Gpi2 and Gpi3 proteins, respectively. Human GlcNAc-PI synthase contains two further subunits, Pig-Hp and PigPp. We report that the essential YNL038w gene encodes the S. cerevisiae homologue of Pig-Hp. Haploid YNL038w-deletion strains were created, in which Ynl038wp could be depleted by repressing YNL038w expression using the GAL10 promoter. Depletion of Ynl038wp from membranes virtually abolished in vitro GlcNAc-PI synthetic activity, indicating that Ynl038wp is necessary for GlcNAc-PI synthesis in vitro. Further, depletion of Ynl038wp in an smp3 mutant background prevented the formation of the trimannosylated GPI intermediates that normally accumulate in this late-stage GPI assembly mutant. Ynl038wp is therefore required for GPI synthesis in vivo. Because YNL038w encodes a protein involved in GPI biosynthesis, we designate the gene GPI15. Potential Pig-Hp/Gpi15p counterparts are also encoded in the genomes of Schizosacchomyces pombe and Candida albicans.
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|Evidence ID||Analyze ID||Gene||Gene Systematic Name||Gene Ontology Term||Gene Ontology Term ID||Qualifier||Aspect||Method||Evidence||Source||Assigned On||Annotation Extension||Reference|
|Evidence ID||Analyze ID||Gene||Gene Systematic Name||Phenotype||Experiment Type||Experiment Type Category||Mutant Information||Strain Background||Chemical||Details||Reference|
|Evidence ID||Analyze ID||Regulator||Regulator Systematic Name||Target||Target Systematic Name||Experiment||Assay||Construct||Conditions||Strain Background||Reference|