| Interaction of Helicobacter pylori with sialylated carbohydrates: The dependence on different parts of the binding trisaccharide Neu5Ac{alpha}3Gal{beta}4GlcNAc (2005) | |||||||||||||
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| 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 (Miller- Podraza et al., 2004). In this paper we investigated the importance of GlcNAc in the binding trisaccharide Neu5Acα3Galβ4GlcNAc and the role of the N-acetamido groups of both Neu5Ac and GlcNAc. An important part of the work was epitope dissection, i.e. chemical derivatizations of the active carbohydrate followed by binding studies. In addition we have 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 while Neu5Acα3Gal turned out to be active. The binding preference for neolacto structures was confirmed, although one strain was also 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. | |||||||||||||
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