KEY PROCESSES IN ER

• Protein glycosylation
• Protein folding

N-GLYCOSYLATION

• Is an ER event
• Is a Co-translational event.
• Occurs on Asn-X-Ser/Thr residues

O-linked glycosylation occurs in the Golgi apparatus

EVENTS OF N-GLYCOSYLATION

• Nascent protein imports co-translationally through translocon.
• Oligosaccharyl transferase transfers oligossacharide from dolichol to N-side group of Asn residue
• 3 sugars trimmed from the 14 sugar oligossacharide as protein exits translocon.
• Chaperones help protein fold in lumen