Intracellular functions of N-linked glycans

N-Linked oligosaccharides arise when blocks of 14 sugars are added cotransl ationally to newly synthesized polypeptides in the endoplasmic reticulum (E R), These glycans are then subjected to extensive modification as the glyco proteins mature and move through the ER via the Golgi complex to their fina l destinations inside and outside the cell. in the ER and in the early secr etory pathway, where the repertoire of oligosaccharide structures is still rather small, the glycans play a pivotal role in protein folding, oligomeri zation, quality control, sorting, and transport. They are used as universal "tags" that allow specific Lectins and modifying enzymes to establish orde r among the diversity of maturing glycoproteins. in the Golgi complex, the glycans acquire more complex structures and a new set of functions. The div ision of synthesis and processing between the ER and the Golgi complex repr esents an evolutionary adaptation that allows efficient exploitation of the potential of oligosaccharides.