Quantitative oligosaccharide profiles were determined for each of 18 human IgG paraproteins representing the four subclasses. Each paraprotein exhibits a unique profile that may be substantially different from that observed for polyclonal IgG. The IgG2 and some IgG3 proteins analysed exhibit a predominance of oligosaccharide moieties having galactose on the Man(alpha 1----3) arm rather than the Man(alpha 1----6) arm; it was previously held that galactosylation of the Man(alpha 1----6) arm is preferred, as observed for IgG1, IgG4 and polyclonal IgG. An IgG4 protein is reported that has galactosylated Man(alpha 1----3) and Man(alpha 1----6) arms on both Fc-localized carbohydrate moieties; previous findings suggested that such fully glycosylated structures could not be accommodated within the internal space of the C gamma 2 domains. Unusual monoantennary oligosaccharides present in IgG2 and IgG3 proteins were isolated and their structures determined.
A comparative study of the N-linked oligosaccharide structures of human IgG subclass proteins
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R Jefferis, J Lund, H Mizutani, H Nakagawa, Y Kawazoe, Y Arata, N Takahashi; A comparative study of the N-linked oligosaccharide structures of human IgG subclass proteins. Biochem J 15 June 1990; 268 (3): 529–537. doi: https://doi.org/10.1042/bj2680529
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