Structure of the oligosaccharides sensitive to endo‐β‐N‐acetylglucosaminidase H in the glycoprotein of Friend murine leukemia virus

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Abstract
The surface glycoprotein (mixture of isoglycoproteins with MW 69,000 and 71,000) was isolated from the particles of Friend murine leukemia virus, and was successively digested with protease and with endo-.beta.-N-acetylglucosaminidase from Streptomyces griseus. Roughly 20% (wt/wt) of the carbohydrates in this glycoprotein were thus released, and they were fractionated by high-performance liquid chromatography after reduction with KB3H4/NaBH4. The radioactive oligosaccharitol fractions obtained were analyzed by exoglycosidase digestion, by acetolysis and, after permethylation, by fast atom-bombardment mass spectrometry, as well as by capillary GLC/mass spectrometry following hydrolysis, reduction and peracetylation. Around 85% (mol/mol) of the endo-H-sensitive viral glycans were thus found to be oligomannosidic oligosaccharitols of size classes Man5GlcNAcOH, Man6GlcNAcOH, Man8GlcNAcOH, Man7GlcNAcOH and Man9GlcNAcOH (in order of prevalence), and the major structural isomers of each size class were identified. About another 15% (mol/mol) of the oligosaccharitols were shown to be of the mixed type, comprising mainly 4 species in which the Man(.alpha.1 .fwdarw. 6)-branch of the Man.alpha.1 .fwdarw. 6(Man.alpha.1 .fwdarw. 3) Man.beta.1 .fwdarw. 4GlcNAcOH core is substituted by 1 or 2 additional .alpha.-mannoses, while the Man(.alpha.1 .fwdarw. 3)-branch carries an N-acetyllactosamine unit substituted by sialic acid, or by Gal(.alpha.1 .fwdarw. 3).
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