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

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 Cs 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-acetylneuramipic acid Wheat-germ agglutinin is a plant lectin which agglutinates various types of animal cells, of malignant cells and of protease-treated cells [l-31. The agglutination of cells is inhibited by N-acetylglucosamine and its /3l-4 oligomers [2,4]. In addition, wheat-germ agglutinin has been claimed to bind N-acetylneuraminic acid on the basis of equilibrium dialysis [5] and nuclear magnetic resonance [6] studies. Furthermore, the agglutination of neuraminidasetreated cells usually requires a higher concentration of wheat-germ agglutinin than required for untreated cells [2,7] although in some instances the neuraminidase treatment does not lower the cell agglutinability by the lectin [8]. Immobilized wheat germ agglutinin binds membrane sialoglycoproteins [9,10] but fails to bind the related sialoglycopeptides [9]. In the present paper, we wish to report several data showing that N-acetylneuraminic acid, gangliosides and glycoAbbreviations. Glc, glucose; Gal, galactose, NeuAc, N-acetylneuraminic acid ; NeuGc, N-glycoloylneuraminic acid ; Cer, ceramide; GM3, NeuAca2+3Gal~l+4GlcCer; GMz, GalNAc(3tZa-NeuAc)~l+4Gal~1+4GlcCer; GMI, Ga1/31+ 3GalNAc(3+2a-N e u A c )~l + 4 G a l~I -4GlcCer; GDI,, NeuAca2-3GalP1+3-GalNAc(3t2ctNeuAc)fll+4Gal~1-r4GlcCer; GDlb, Galpl -r 3-GalNAc(3+2aNeuAcXt2aNeuAc)~l+4Gal~I + 4GlcCer; GTl, NeuAcn2+ 3Gal/1'1+ 3GalNAc(3 + 2aNeuAcX t 2aNeuAc)flI -j 4-Gal81 +4GlcCer, Nph, p-nitrophenyl-.

Wheat germ agglutinin: effects of limited reduction of the disulfide bonds and carboxymethylation on the properties of the lectin

“…It is possible that the disulfide bonds are formed on the nascent polypeptide chain, each time the translation of a domain is completed. This would agree with the observation of spontaneous refolding and reoxidation of reduced erabutoxin [24] which has a folding pattern equivalent to that of one of the 4 homologous domains of WGA [7,10].…”

“…The lectin isolated from lliticum vulgare (WGA) consists of two protomers of 164 amino acid residues each [3-51. It specifically binds GlcNAc or its /31+4-linked di-and trisaccharides [3] as well as sialic acid [6,7] and contains 4 binding sites for these ligands [5-91. Each protomer consists of 4 structural domains containing 41 amino acid residues, among them 8 cysteines forming 4 intradomain disulfide bridges [3,8,10].…”

Histochemical detection of the lectin-binding carbohydrates in the zona pellucida during oocyte growth in the wild boar (Sus scrofa scrofa)

“…Staining with WGA and RCA-I but not with GSA-II, suggests that N-acetylglucosamine occupied an internal rather than terminal position. The absence of any reduction of WGA labelling by sialidase degradation, even after saponification, indicates that sialic acid did not compete with N-acetylglucosamine for WGA [10].…”

The interaction ofTrypanosoma congolensewith endothelial cells

“…Cells were washed extensively with PBS before applying the trypanosomes. (ii) Lectin binding: BAE monolayers were incubated for 45 min at 37 °C in PBS with SO^g/ml of the following lectins: wheat germ agglutinin (WGA), specific for JV-acetyl-glucosamine and iV-acetyl-neuraminic acid residues, succinylated WGA (Vector Laboratories, England), specific for iV-acetyl-glucosamine only (Monsigny et al 1980), Tetragonolobus purpurea agglutinin (TPA), specific for fucosyl residues, Concanavalin A (Con A), specific for D-mannosyl and D-glucosyl residues, and soybean agglutinin Drug treatments. Trypanosomes (10 6 /ml) were incubated in PBS/0-5% BSA in the presence of 10-100 mM deoxyglucose for 20 min at room temperature.…”