Abstract
The present paper describes the structures of the N-linked oligosaccharides of the human-immunodeficiency-virus (HIV) envelope glycoprotein gp120 (cloned from the HTLV-III B isolate and expressed as a secreted fusion protein after transfection of Chinese-hamster ovary cells), which is known to bind with high affinity to human T4-lymphocytes. Oligosaccharides were released from peptide by hydrazinolysis, fractionated by paper electrophoresis, high-performance lectin-affinity chromatography and Bio-Gel P-4 column chromatography, and their structures determined by sequential exoglycosidase digestions in conjunction with methylation analysis. The glycoprotein was found to be unique in its diversity of oligosaccharide structures. These include high-mannose type and hybrid type, as well as four categories of complex-type chains: mono-, bi-, tri- and tetra-antennary, with or without N-acetyl-lactosamine repeats, and with or without a core-region fucose residue. Among the sialidase-treated oligosaccharides, no less than 29 structures were identified as follows: (formula; see text) where G is galactose, GN is N-acetylglucosamine, M is mannose, F is fucose, and '+/- ' means that residues are present in a proportion of chains. The actual number of oligosaccharide structures is much greater, since before desialylation there was evidence that, among the hybrid and complex-type chains, all but 6% contained sialic acid at the C-3 position of terminal galactose residues, and partially sialylated forms of the bi- and multi-antennary chains were present. Detailed evidence for the proposed oligosaccharide sequences will be published as a supplementary paper [T. Mizuochi, M. W. Spellman, M. Larkin, J. Solomon, L. J. Basa & T. Feizi (1988) Biomed. Chromatogr., in the press].