Oligosaccharyltransferase (OST) is an integral membrane protein that catalyzes N-linked glycosylation of nascent proteins in the lumen of the endoplasmic reticulum. Although the yeast OST is an octamer assembled from nonhomologous subunits (Ost1p, Ost2p, Ost3p/Ost6p, Ost4p, Ost5p, Wbp1p, Swp1p, and Stt3p), the composition of the vertebrate OST was less well defined. The roles of specific OST subunits remained enigmatic. Here we show that genomes of most multicellular eukaryotes encode two homologs of Stt3p and mammals express two homologs of Ost3p. The Stt3p and Ost3p homologs are assembled together with the previously described mammalian OST subunits (ribophorins I and II, OST48, and DAD1) into complexes that differ significantly in enzymatic activity. Tissue and cell type-specific differences in expression of the Stt3p homologs suggest that the enzymatic properties of oligosaccharyltransferase are regulated in eukaryotes to respond to alterations in glycoprotein flux through the secretory pathway and may contribute to tissue-specific glycan heterogeneity.
|Evidence ID||Analyze ID||Interactor||Interactor Systematic Name||Interactor||Interactor Systematic Name||Type||Assay||Annotation||Action||Modification||Phenotype||Source||Reference||Note|
|Evidence ID||Analyze ID||Gene||Gene Systematic Name||Gene Ontology Term||Gene Ontology Term ID||Qualifier||Aspect||Method||Evidence||Source||Assigned On||Reference||Annotation Extension|
|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||Conditions||Strain||Source||Reference|