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Branch-specific sialylation of IgG-Fc glycans by ST6Gal-I

Adam W Barb1, Evan K Brady, James H Prestegard

  • 1Complex Carbohydrate Research Center, 315 Riverbend Road, University of Georgia, Athens, Georgia 30602, USA.

Biochemistry
|September 24, 2009
PubMed

Sialylated forms of the Fc fragment of immunoglobulin G, produced by the human alpha2-6 sialyltransferase ST6Gal-I, were identified as potent anti-inflammatory mediators in a mouse model of rheumatoid arthritis and are potentially the active components in intravenous IgG anti-inflammatory therapies. The activities and specificities of hST6Gal-I are, however, poorly characterized. Here MS and NMR methodology demonstrates glycan modification occurs in a branch-specific manner with the alpha1-3Man branch of the complex, biantennary Fc glycan preferentially sialylated. Interestingly, this substrate preference is preserved when using a released glycan, suggesting that the apparent occlusion of glycan termini in Fc crystal structures does not dominate specificity.

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