Protein Glycosylation in Aspergillus fumigatus Is Essential for Cell Wall Synthesis and Serves as a Promising Model of Multicellular Eukaryotic Development

Figure 1

Biosynthesis of the lipid-bound oligosaccharide and transfer of the oligosaccharide to the nascent polypeptide in the endoplasmic reticulum of S. cerevisiae. The identified ALG genes for the respective glycosylation reactions are indicated. Synthesis starts at the cytoplasmic face with UDP-GlcNAc and GDP-Man as donors. The Man₅GlcNAc₂-PP-Dol is then transferred to the luminal side with the help of Rft1 and elongated to the full-length lipid-linked oligosaccharide Glc₃Man₉GlcNAc₂-PP-Dol by using Dol-P-Man and Dol-P-Glc as donors. The oligosaccharide is subsequently transferred to the γ-amido group of the asparagine residues within the consensus sequence Asn-X-Ser/Thr of nascent secretory proteins. This reaction is catalyzed by the oligosaccharyltransferase (OST) complex.