Carbohydrate receptor specificity of K99 fimbriae of enterotoxigenicEscherichia coli |
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Authors: | Mats Lindahl Reinhard Brossmer Torkel Wadström |
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Affiliation: | (1) Department of Veterinary Microbiology, Swedish University of Agricultural Sciences, Biomedicum, Box 583, S-751 23 Uppsala, Sweden;(2) Institut für Biochemie II, Universität Heidelberg, Im Neuenheimer Feld 328, 6900 Heidelberg 1, W. Germany |
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Abstract: | K99 Fimbriae from enterotoxigenicEscherichia coli (ETEC) were found to bind specifically to sialic acid, as measured in a haemagglutination inhibition assay using the intact bacteria and human erythrocytes. The affinity forN-glycolylneuraminic acid was about twice that ofN-acetylneuraminic acid (NeuAc), and other monosaccharides were found to be at least ten-fold less effective as inhibitors. The specificity was found to depend on electrostatic interaction where the carboxyl group and its orientation plays an important role. 2--Benzyl-NeuAc was a better inhibitor than 2--methyl-NeuAc suggesting a hydrophobic patch near the binding site on the protein. Axially oriented hydroxyl groups as in 4-epi-NeuAc and 3-hydroxy-NeuAc seemed to participate in binding since these derivatives were better inhibitors thanN-acetylneuraminic acid. K99 was found to have a higher affinity for 4-O-acetyl-NeuAc and lower affinity forN-acetylneuraminic acid withO-substituents at C7-C9 as compared toN-acetylneuraminic acid. Hence, the degree ofO-acetylation of sialic acid in the mucosa of the small intestine may influence colonization and determine susceptibility to infection. |
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Keywords: | carbohydrate receptor E.coli K99 sialic acid |
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