The majority of proteins that traverse the secretory pathway receive asparagine (Asn)-linked glycosylations.
Glycans are bulky hydrophilic modifications that serve a variety of structural and functional roles within the cell.
The role of Asn-linked glycans is proteic maturation and quality-control protein tags in the early secretory pathway.
The carbohydrate composition encodes crucial information about the structure, localization and age of glycoproteins.
The "glycan code" is encoded by a series of glycosidases and carbohydrate transferases that line the secretory pathway.
This code is deciphered by carbohydrate-binding proteins that possess distinct carbohydrate binding properties and act as molecular chaperones or sorting receptors.
These glycosidases and transferases work in concert with resident secretory pathway carbohydrate-binding proteins to form a network that assists in the maturation and trafficking of both native and aberrant glycoproteins within the cell.
References
Hebert DN, Garman SC, Molinari M. The glycan code of the endoplasmic reticulum: asparagine-linked carbohydrates as protein maturation and quality-control tags. Trends Cell Biol. 2005 Jul;15(7):364-70. PMID: 15939591