3. Protein N-glycosylation in animal cells

3.1 Glycoprotein biosynthesis in animal cells

Glycoproteins are assembled first in the endoplasmic reticulum (ER) and then in the Golgi apparatus. Glycoproteins are generally secreted, membrane or resident proteins of these two compartments, which implies that they possess a signal sequence governing their translocation to the ER.

The synthesis of an N-glycosylprotein requires the prior elaboration of a glycan consisting of fourteen monosaccharides on a polyisoprenic lipid embedded in the ER membrane, dolichol phosphate (Dol-P). Assembly of the oligosaccharide takes place sequentially via a very specific metabolic cycle known as the "dolichol cycle"