title: Structure of the oligosaccharyl transferase complex at 12 A resolution.
abstract: Oligosaccharyl transferase (OT) catalyzes the transfer of a lipid-linked oligosaccharide to the nascent polypeptide emerging from the translocon. Currently, there is no structural information on the membrane-embedded OT complex, which consists of eight different polypeptide chains. We report a 12 A resolution cryo-electron microscopy structure of OT from yeast. We mapped the locations of four essential OT subunits through a maltose-binding protein fusion strategy. OT was found to have a large domain in the lumenal side of endoplasmic reticulum where the catalysis occurs. The lumenal domain mainly comprises the catalytic Stt3p, the donor substrate-recognizing Wbp1p, and the acceptor substrate-recognizing Ost1p. A prominent groove was observed between these subunits, and we propose that the nascent polypeptide from the translocon threads through this groove while being scanned by the Ost1p subunit for the presence of the glycosylation sequon.
authors.affiliation: Biology Department, Brookhaven National Laboratory, Upton, NY 11973-5000, USA.
authors.forename: Hua
authors.initials: H
authors.lastname: Li
authors.forename: Manasi
authors.initials: M
authors.lastname: Chavan
authors.forename: Hermann
authors.initials: H
authors.lastname: Schindelin
authors.forename: William J
authors.initials: WJ
authors.lastname: Lennarz
authors.forename: Huilin
authors.initials: H
authors.lastname: Li
mesh_terms: D002352:Carrier Proteins / Q000235:genetics; D003001:Cloning, Molecular; D020285:Cryoelectron Microscopy; D004072:Digitonin / Q000494:pharmacology; D006602:Hexosyltransferases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional; D058619:Maltose-Binding Proteins; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008954:Models, Biological; D008958:Models, Molecular; D008970:Molecular Weight; D046912:Multiprotein Complexes / Q000737:chemistry; D021122:Protein Subunits / Q000737:chemistry; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics; D012995:Solubility / Q000187:drug effects; D015003:Yeasts / Q000201:enzymology
chemical_list: D002352:Carrier Proteins; D058619:Maltose-Binding Proteins; D008565:Membrane Proteins; D046912:Multiprotein Complexes; D021122:Protein Subunits; D011993:Recombinant Fusion Proteins; D006602:Hexosyltransferases; C025620:dolichyl-diphosphooligosaccharide - protein glycotransferase; D004072:Digitonin