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.
Scott
Daniel C
DC
Department of Molecular and Cell Biology and Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, CA 94720, USA.
Schekman
Randy
R
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