Glycobiology Advance Access originally published online on January 19, 2005
Glycobiology 2005 15(6):625-636; doi:10.1093/glycob/cwi044
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Glycobiology vol. 15 no. 6 © Oxford University Press 2005; all rights reserved.
Interaction of Helicobacter pylori with sialylated carbohydrates: the dependence on different parts of the binding trisaccharide Neu5Ac
3Galß4GlcNAc
Institute of Medical Biochemistry, Göteborg University, PO Box 440, SE 405 30 Göteborg, Sweden
1 To whom correspondence should be addressed; e-mail: petra.johansson{at}medkem.gu.se
Received on October 12, 2004; revised on December 23, 2004; accepted on January 17, 2005
We have recently shown that binding of Helicobacter pylori to sialylated carbohydrates is dependent on the presence of the carboxyl group and the glycerol chain of Neu5Ac. In this work we investigated the importance of GlcNAc in the binding trisaccharide Neu5Ac
3Galß4GlcNAc and the role of the N-acetamido groups of both Neu5Ac and GlcNAc. An important part of the project was epitope dissection, that is chemical derivatizations of the active carbohydrate followed by binding studies. In addition we used a panel of various unmodified carbohydrate structures in the form of free oligosaccharides or glycolipids. These were tested for binding by hemagglutination inhibition assay, TLC overlay tests, and a new quantitative approach using radiolabeled neoglycoproteins. The studies showed that the N-acetamido group of Neu5Ac is important for binding by H. pylori, whereas the same group of GlcNAc is not. In addition, Fuc attached to GlcNAc, as tested with sialyl-Lewis x, did not affect the binding. Free Neu5Ac was inactive as inhibitor, and Neu5Ac3Gal turned out to be active. The binding preference for neolacto structures was confirmed, although one strain also was inhibited by lacto chains. The combined results revealed that an intact Neu5Ac is crucial for the interactions with H. pylori. Parts of Gal also seem to be necessary, whereas the role of the GlcNAc is secondary. GlcNAc does influence binding, however, primarily serving as a guiding carrier for the binding epitope rather than being a part of the binding structure.
Key words: De-N-acetylation / glycosphingolipids / Helicobacter pylori / sialic acid
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