The molecular size of glycans liberated by hydrazinolysis from semliki forest virus proteins

Abstract

The glycans of well characterized, [6- 3H]galactose-labelled glycopeptides, GC-4 from bovine IgG 1 as well as GP-V-2 and GP-V-5 from α 1-acid glycoprotein, were liberated by hydrazinolysis. Molecular weights close to the expected values were observed by gel filtration. Desialated glycans of Semliki Forest virus proteins were likewise liberated by hydrazinolysis and subjected to gel filtration. Metabolically labelled [1- 3H]galactose-oligosaccharides of the mixed viral proteins revealed an apparent molecular weight of 1800. The bi-antennary glycan liberated from the reference glycopeptide GC-4 was of 1750 daltons. A mixture of [2- 3H]mannose-labelled E 1-and E 2-proteins of the virus contained L-type glycans of 1800 daltons (formerly called A-type), and M-type glycans of 1200 daltons (formerly called B-type). A fraction of the E 3-glycans isolated by affinity chromatography on Concanavalin A-Sepharose showed an average molecular weight of 2150, a value intermediate between the three- and four-antennary glycans liberated from the reference glycopeptides GP-V-5 and GP-V-2. The rest of the E 3-glycans were of 1850 daltons, a value close to the bi-antennary GC-4 glycan. We suggest that the comparatively large size of the E 3-glycans and the exposed position of E 3-proteins on the viral surface may be interrelated.