Sugar‐Lectin Interactions: How Does Wheat‐Germ Agglutinin Bind Sialoglycoconjugates?

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Abstract
The specific binding of N‐acetylneuraminic acid to wheat‐germ agglutinin is based on configurational similarities between N‐acetylneuraminic acid and N‐acetylglucosamine. The N‐acetamido group and an adjacent hydroxyl group, both in an equatorial position are shown to be the main determinants. The N‐acetylneuraminic acid–wheat‐germ agglutinin interaction is increased by the removal of the last two carbons C8 and C9. The interaction between wheat‐germ agglutinin and glycoconjugates containing N‐acetylneuraminic acid is shown to be dependent on a charge effect and on an avidity effect. Succinylated wheat‐germ agglutinin which is negatively charged at physiological pH, in contrast with wheat‐germ agglutinin which is positively charged, does not bind cell surface glycoconjugates containing N‐acetylneuraminic acid but does bind cell surface glycoconjugates containing N‐acetylglucosamine. The use of wheat‐germ agglutinin and of succinylated wheat‐germ agglutinin leads to the determination of the number of cell surface receptors containing N‐acetylneuraminic acid.