Comparative analysis of the oligosaccharide donors (Lipid-linked oligosaccharides) for the n-oligosaccharyl transfer reaction

The glycosylation on asparagine residues is one of the ubiquitous protein modifications occurring in the three domains of life. An oligosaccharide chain is preassembled on a lipid-phospho carrier, which is referred to as lipid-linked oligosaccharide (LLO), and transferred to asparagine residues in polypeptide chains by the action of a membrane-bound enzyme, oligosaccharyltransferase. The oligosaccharide donor for the oligosaccharyl transfer reaction is dolichol–diphosphate–oligosaccharide in Eukarya, and polyprenol–diphosphate–oligosaccharide in Eubacteria. The oligosaccharide donor of an archaeal species was reported as dolichol–monophosphate–oligosaccharide. Thus, the difference in the number of phosphate groups aroused interest in whether the use of the monophosphate type donor is widespread in the domain Archaea. In this study, we selected four archaeal species to widely sample the domain Archaea. We used normal-phase liquid chromatography to purify the LLO from cultured archaeal cells and performed ESI-MS analysis to determine the chemical structure of the lipid-phospho part. We found that two euryarchaeal oligosaccharide donors of more ancient origin were a dolichol-monophosphate type, whereas the two crenarchaeal oligosaccharide donors of closer origin to Eukarya were a dolichol–diphosphate type. The present comparative study provides a new insight into the evolution of the oligosaccharide donor in the N-glycosylation system.