title: Polypeptide-binding proteins mediate completion of co-translational protein translocation into the mammalian endoplasmic reticulum.
abstract: The first step in the secretion of most mammalian proteins is their transport into the lumen of the endoplasmic reticulum (ER). Transport of pre-secretory proteins into the mammalian ER requires signal peptides in the precursor proteins and a protein translocase in the ER membrane. In addition, hitherto unidentified lumenal ER proteins have been shown to be required for vectorial protein translocation. This requirement was confirmed in this study by using proteoliposomes that were made from microsomal detergent extracts and contained either low or high concentrations of lumenal ER proteins. Furthermore, immunoglobulin-heavy-chain-binding protein (BiP) was shown to be able to substitute for the full set of lumenal proteins and, in the case of biotinylated precursor proteins, avidin was found to be able to substitute for lumenal proteins. Thus, the polypeptide-chain-binding protein BiP was identified as one lumenal protein that is involved in efficient vectorial protein translocation into the mammalian ER.
authors.affiliation: Medizinische Biochemie, Universität des Saarlandes, D-66421 Homburg, Germany.
authors.forename: Jens
authors.initials: J
authors.lastname: Tyedmers
authors.forename: Monika
authors.initials: M
authors.lastname: Lerner
authors.forename: Martin
authors.initials: M
authors.lastname: Wiedmann
authors.forename: Jörg
authors.initials: J
authors.lastname: Volkmer
authors.forename: Richard
authors.initials: R
authors.lastname: Zimmermann
mesh_terms: D000818:Animals; D001360:Avidin / Q000737:chemistry / Q000378:metabolism; D001665:Binding Sites; D019921:Biotinylation; D004285:Dogs; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D000091342:Endoplasmic Reticulum Chaperone BiP; D006360:Heat-Shock Proteins / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism; D008861:Microsomes / Q000737:chemistry / Q000378:metabolism*; D018832:Molecular Chaperones / Q000378:metabolism*; D014176:Protein Biosynthesis; D011499:Protein Processing, Post-Translational; D021381:Protein Transport; D011510:Proteolipids / Q000737:chemistry / Q000378:metabolism; D000069816:SEC Translocation Channels
chemical_list: D000091342:Endoplasmic Reticulum Chaperone BiP; D006360:Heat-Shock Proteins; D008565:Membrane Proteins; D018832:Molecular Chaperones; D011510:Proteolipids; D000069816:SEC Translocation Channels; C020485:proteoliposomes; D001360:Avidin