Sequence Analysis of Lactosamine Type Glycans of Individual Membrane Proteins of Semliki Forest Virus

3H-fucose and 14C-glucosamine labelled glycopeptides of the individual membrane proteins E1, E2 and E3 of Semliki Forest virus could be sequentially digested with α-neuraminidase, β-galactosidase, N-acetyl-β-glucosaminidase, α- and β-mannosidase, N-acetyl-β-hexosaminidase and finally with α-fucosidase. The degradations of the virus glycopeptides proceeded in the same way as stepwise digestions of reference glycopeptides of the lactosamine type obtained from IgG and α1-acid glycoprotein. This suggests that all three membrane glycoproteins of Semliki Forest virus contained glycans with a monosaccharide sequence characteristic for lactosamine type oligosaccharides. The number of both distal and proximal N-acetyl-glucosamine residues was estimated to be usually two. According to exo- and endo-glycosidase digestions, fucose seemed to be attached to the innermost N-acetyl-glucosamine unit.