> See also: > - [[Post-Translational Modifications]] > - [[Carbohydrates]] # Protein Glycosylation can occur in the endoplasmic reticulum or golgi apparatus - remember the smooth vs rough er; the “rough" in the name refers to the ribosom There are several types of glycosylation: - O-linked - N-L Note that C- and N-glycosylation do not refer to the terminal ends of the polypeptide and instead refer to the type of glycosidic bond being formed. ### O-Glycosylation O-linked oligosaccharides are attached to proteins *post-translationally* one sugar at a time in the [[The Endomembrane System|Golgi apparatus]]. Added to the -OH group of *Serine* or *Threonine* residues ### N-Glycosylation ![[Pasted image 20231017211017.png|200]] Attaches to asparagine in a specific c Asn - $X$ - Ser/Thr (Where $X \ne$ Pro) Occurs co-translationally in the endoplasmic reticulum and then post-translationally in the golgi apparatus The first step is to attach a 14-mer oligosaccharide to the asparagine residue ### C-Mannosylation