title: Distinct processes mediate glycoprotein and glycopeptide export from the endoplasmic reticulum in Saccharomyces cerevisiae.
abstract: Protein and peptide export from the Saccharomyces cerevisiae endoplasmic reticulum was examined in vitro using the secretory protein pro-alpha-factor and a synthetic tripeptide containing the acceptor site for N-linked glycosylation as substrates. The release of both glycosylated pro-alpha-factor and glycotripeptide from the endoplasmic reticulum was dependent on cytosol, temperature, and ATP. Antibodies against two proteins essential for the formation of transport vesicles, Sec23p and p105, inhibited glyco-pro-alpha-factor exit from the endoplasmic reticulum but did not affect the release of the glycosylated tripeptide. Furthermore, in contrast to pro-alpha-factor, the exported glycopeptide was not associated with a membrane fraction and did not acquire Golgi-specific alpha(1-6)-linked mannose residues. We conclude that the glycosylated tripeptide leaves the yeast endoplasmic reticulum by a route different from the secretory pathway, possibly through an ATP-driven pump.
authors.affiliation: Department of Molecular and Cell Biology, University of California, Berkeley 94720.
authors.forename: K
authors.initials: K
authors.lastname: Römisch
authors.forename: R
authors.initials: R
authors.lastname: Schekman
mesh_terms: D000595:Amino Acid Sequence; D000906:Antibodies; D001692:Biological Transport; D003600:Cytosol / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D005656:Fungal Proteins / Q000378:metabolism; D006020:Glycopeptides / Q000378:metabolism*; D006023:Glycoproteins / Q000378:metabolism*; D006031:Glycosylation; D006056:Golgi Apparatus / Q000378:metabolism; D007700:Kinetics; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D013462:Sulfur Radioisotopes; D013696:Temperature
chemical_list: D000906:Antibodies; D005656:Fungal Proteins; D006020:Glycopeptides; D006023:Glycoproteins; D009842:Oligopeptides; D013462:Sulfur Radioisotopes