Dolichol-linked oligosaccharides

Glycosyladon of the p62 afad El proteins is not needed for correct assembly in the ER, since in tunicamycin-treated cells, the assembly of these nonglycosylated proteins proceeds normally (Garoff and Schwarz, 1978). The drug tunicamycin blocks the assembly of the dolichol-linked oligosaccharide intermediate so that no transfer of oligosaccharides to nascent protein is possible (Tkasz and Lampen, 1975). 

The biological function of this dolichol-linked oligosaccharide was revealed in pulse-chase experiments which showed that the intact oligosaccharide was transferred, as such, to protein. Subsequent studies, to be discussed, confirmed that the formation of the oligosaccharide linked to the Asn residues of glycoproteins is probably initiated by transfer of the oligosaccharide from the dolichol diphosphate intermediate to the asparagine residue of a nascent polypeptide (see Refs. 35, 49, 50, and 67 for reviews). 

Synthesis of the dolichol-linked oligosaccharide. The reaction starts on the cytosolic side of the endoplasmic reticulum. Seven single-step reactions lead to the heptasaccharide that is linked to dolichol... 

Fig. 2. Pathway of biosynthesis of the dolichol-linked oligosaccharide. n-UDP GlcNAc-Uridine diphosphate n-PPDol GlcNAc-Pyrophosphatedolichol 0-GDP Man-Guanosine diphosphate O-Pdol Man-Phosphodolichol -Pdol Glc-Phosphodolichol. (adopted from [32])...

Burda P, Borsig L, de Rijk - van Andel J, et al. A novel carbohydrate-deficient glycoprotein syndrome characterized by a deficiency in glucosylation of the dolichol-linked oligosaccharide. / Clin Invest 1998 102 647-652. 

Krasnewich, D.M. Holt, G. D. Brantly, M. Skovby, F. Redwine, J. Gahl, W. A. Abnormal synthesis of dolichol-linked oligosaccharides in carbohydrate-deficient glycoprotein syndrome. Glycobiology 1995, 5, 503-510. 

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