Glycan structure and site of glycosylation in the ER-resident glycoprotein, uridine 5′-diphosphate-glucose: glycoprotein glucosyltransferases 1 from rat, porcine, bovine, and human

• Glycan structure of ER-resident sensor glycoprotein UGGT1 was investigated.
• Site of glycosylation in UGGT1 was revealed to be Asn269.
• Glycan structures at Asn269 in UGGT1 were shown to be Hex5–8HexNAc2.
• The profile of glycan compositions in four species were investigated.

Here we report glycan structures and their position of attachment to a carrier protein, uridine 5′-diphosphate-glucose: glycoprotein glucosyltransferase (UGGT1), as detected using tandem mass spectrometry. UGGT1 acts as a folding sensor of newly synthesized glycosylated polypeptides in the endoplasmic reticulum, and the transferase itself is known to be glycosylated. The structure of glycan attached to UGGT1, however, has not been investigated. In this study, we reveal the site of glycosylation (N269) and the glycan structures (Hex5–8HexNAc2) in UGGT1 obtained from rat (Rattus norvegicus), pig (Sus scrofa), cow (Bos taurus), and human (Homo sapiens).