Role of Sec61p in the ER-associated degradation of short-lived transmembrane proteins.
Misfolded proteins in the endoplasmic reticulum (ER) are identified and degraded by the ER-associated degradation pathway (ERAD), a component of ER quality control. In ERAD, misfolded proteins are removed from the ER by retrotranslocation into the cytosol where they are degraded by the ubiquitin-proteasome system. The identity of the specific protein components responsible for retrotranslocation remains controversial, with the potential candidates being Sec61p, Der1p, and Doa10. We show that the cytoplasmic N-terminal domain of a short-lived transmembrane ERAD substrate is exposed to the lumen of the ER during the degradation process. The addition of N-linked glycan to the N terminus of the substrate is prevented by mutation of a specific cysteine residue of Sec61p, as well as a specific cysteine residue of the substrate protein. We show that the substrate protein forms a disulfide-linked complex to Sec61p, suggesting that at least part of the retrotranslocation process involves Sec61p.
Department of Molecular and Cell Biology and Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, CA 94720, USA.
Daniel C
DC
Scott
Randy
R
Schekman
D003545:Cysteine / Q000378:metabolism; D004220:Disulfides / Q000378:metabolism; D004586:Electrophoresis; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D006031:Glycosylation; D019751:Intramolecular Transferases; D008565:Membrane Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D026901:Membrane Transport Proteins; D008954:Models, Biological; D050505:Mutant Proteins / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D011499:Protein Processing, Post-Translational; D021381:Protein Transport; D000069816:SEC Translocation Channels; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D013379:Substrate Specificity; D013997:Time Factors
D004220:Disulfides; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D050505:Mutant Proteins; D000069816:SEC Translocation Channels; C499383:SEC61 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D019751:Intramolecular Transferases; C068903:DEG1 protein, S cerevisiae; D003545:Cysteine