Oligosaccharyltransferase activity is associated with a protein complex composed of ribophorins I and II and a 48 kd protein

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Department of Biochemistry and Molecular Biology



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Medical Subject Headings

Amino Acid Sequence; Animals; Binding Sites; Blotting, Western; Chromatography; Consensus Sequence; Dogs; Dolichol; Endoplasmic Reticulum; *Hexosyltransferases; Macromolecular Substances; Membrane Proteins; Molecular Sequence Data; Protein Conformation; Transferases


Oligosaccharyltransferase catalyzes the N-linked glycosylation of asparagine residues on nascent polypeptides in the lumen of the rough endoplasmic reticulum (RER). A protein complex composed of 66, 63, and 48 kd subunits copurified with oligosaccharyltransferase from canine pancreas. The 66 and 63 kd subunits were shown by protein immunoblotting to be identical to ribophorin I and II, two previously identified RER glycoproteins that colocalize with membrane-bound ribosomes. The transmembrane segment of ribophorin I was found to be homologous to a recently proposed dolichol recognition consensus sequence. Based on a revision of the consensus sequence, we propose a model for the interaction of dolichol with the glycosyltransferases that catalyze the assembly and transfer of lipid-linked oligosaccharides.

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Citation: Cell. 1992 Apr 3;69(1):55-65.

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