title: Structure of the mammalian oligosaccharyl-transferase complex in the native ER protein translocon.
abstract: In mammalian cells, proteins are typically translocated across the endoplasmic reticulum (ER) membrane in a co-translational mode by the ER protein translocon, comprising the protein-conducting channel Sec61 and additional complexes involved in nascent chain processing and translocation. As an integral component of the translocon, the oligosaccharyl-transferase complex (OST) catalyses co-translational N-glycosylation, one of the most common protein modifications in eukaryotic cells. Here we use cryoelectron tomography, cryoelectron microscopy single-particle analysis and small interfering RNA-mediated gene silencing to determine the overall structure, oligomeric state and position of OST in the native ER protein translocon of mammalian cells in unprecedented detail. The observed positioning of OST in close proximity to Sec61 provides a basis for understanding how protein translocation into the ER and glycosylation of nascent proteins are structurally coupled. The overall spatial organization of the native translocon, as determined here, serves as a reliable framework for further hypothesis-driven studies.
authors.affiliation: 1] Department of Molecular Structural Biology, Max-Planck Institute of Biochemistry, Am Klopferspitz 18, D-82152 Martinsried, Germany [2].
authors.forename: Stefan
authors.initials: S
authors.lastname: Pfeffer
authors.affiliation: 1] Department of Medical Biochemistry and Molecular Biology, Saarland University, D-66421 Homburg, Germany [2].
authors.forename: Johanna
authors.initials: J
authors.lastname: Dudek
authors.affiliation: Gene Center and Center for integrated Protein Science Munich, Department of Biochemistry, University of Munich, D-81377 Munich, Germany.
authors.forename: Marko
authors.initials: M
authors.lastname: Gogala
authors.affiliation: Department of Medical Biochemistry and Molecular Biology, Saarland University, D-66421 Homburg, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Schorr
authors.affiliation: Department of Medical Biochemistry and Molecular Biology, Saarland University, D-66421 Homburg, Germany.
authors.forename: Johannes
authors.initials: J
authors.lastname: Linxweiler
authors.affiliation: Department of Medical Biochemistry and Molecular Biology, Saarland University, D-66421 Homburg, Germany.
authors.forename: Sven
authors.initials: S
authors.lastname: Lang
authors.affiliation: Gene Center and Center for integrated Protein Science Munich, Department of Biochemistry, University of Munich, D-81377 Munich, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Becker
authors.affiliation: Gene Center and Center for integrated Protein Science Munich, Department of Biochemistry, University of Munich, D-81377 Munich, Germany.
authors.forename: Roland
authors.initials: R
authors.lastname: Beckmann
authors.affiliation: Department of Medical Biochemistry and Molecular Biology, Saarland University, D-66421 Homburg, Germany.
authors.forename: Richard
authors.initials: R
authors.lastname: Zimmermann
authors.affiliation: Department of Molecular Structural Biology, Max-Planck Institute of Biochemistry, Am Klopferspitz 18, D-82152 Martinsried, Germany.
authors.forename: Friedrich
authors.initials: F
authors.lastname: Förster
mesh_terms: D002478:Cells, Cultured; D020285:Cryoelectron Microscopy; D004721:Endoplasmic Reticulum / Q000737:chemistry* / Q000502:physiology; D020868:Gene Silencing / Q000502:physiology; D006031:Glycosylation; D006367:HeLa Cells; D006602:Hexosyltransferases / Q000737:chemistry* / Q000502:physiology; D006801:Humans; D008565:Membrane Proteins / Q000737:chemistry* / Q000502:physiology; D021381:Protein Transport / Q000502:physiology; D034741:RNA, Small Interfering / Q000502:physiology; D000069816:SEC Translocation Channels; D014157:Transcription Factors / Q000737:chemistry* / Q000502:physiology
chemical_list: D008565:Membrane Proteins; D034741:RNA, Small Interfering; D000069816:SEC Translocation Channels; D014157:Transcription Factors; D006602:Hexosyltransferases; C025620:dolichyl-diphosphooligosaccharide - protein glycotransferase