Glycosylation of intracellular Sindbis virus glycoproteins

Oligosaccharides of purified intracellular Sindbis virus glycoproteins have been examined by high-resolution Bio-Gel chromatography. The array of glycopeptides from cellular E1 and E2 appeared similar to the glycopeptides (S1, S2, S3, and S4) found in mature virus glycoproteins described previously [Hakimi, J., & Atkinson, P. H. (1980) Biochemistry 19, 5619]. However, compared to its viral counterpart, intracellular E1 glycoprotein also contained larger sized mannosyl oligosaccharides. B and PE2 proteins were found to contain an array of primarily large mannosyl oligosaccharides (8-10 hexose units). No sialyl glycopeptides were found on these proteins regardless of labeling time. By contrast, the products of PE2 cleavage (E2 and E3) contained sialyl glycopeptides similar to those found in mature virus (S1, S2, and S3). E2 also contained smaller mannosyl oligosaccharides (8-5 hexose units) similar to its viral counterpart. Current evidence shows that sialyl and galactosyl transferases are in or near the Golgi region. Thus we conclude that cleavage of PE2 with a Man8 oligosaccharide structure occurs in the Golgi region and not in the plasma membrane as suggested by others.