Dolichol
Protein glycosylation is an essential step in the formation of membrane proteins. It the process of transformation of precursor oligosaccharide "which is composed of N-acetylglucosamine,mannose and glucose and containing of total of 14 sugar" [1] to proteins in the Endoplasmis Reticulum. This transfer is maintained by oligosaccharyl transferase and the precursor oligosaccharide is provided by the molecule dolichol. Dolichol attaches the precursor oligosaccharide chain to the asparagine. The oligosaccharide chain is linked to dolichol by pyrophosphate bond and this bond is the energy source of the glycosylation process. [2]
References
Alberts B., Johnson A., Lewis J., Raff M., Roberts K., Walter P., (2007) Molecular Biology of the Cell, 5th Edition, New York: Garland Sciences