Proteomics Reveals N-Linked Glycoprotein Diversity in Caenorhabditis elegans and Suggests an Atypical Translocation Mechanism

Protein glycosylation is one of the most common post-translational modifications in eukaryotes and affects various aspects of protein structure and function. To fa-cilitate studies of protein glycosylation, we paired glyco-sylation site-specific stable isotope tagging of lectin af-finity-captured N-linked glycopeptides with mass spectrometry and determined 1,465 N-glycosylated sites on 829 proteins expressed in Caenorhabditis elegans. The analysis shows the diversity of protein glycosylation in eukaryotes in terms of glycosylation sites and oligosac-charide structures attached to polypeptide chains and suggests the substrate specificity of oligosaccharyltrans-ferase, a single multienzyme complex in C. elegans that incorporates an oligosaccharide moiety en bloc to newly synthesized polypeptides. In addition, topological analy