Interaction Of Wheat Germ Agglutinin Research Articles

Lectin-receptor interactions in liposomes II. Interaction of wheat germ agglutinin with phospatidylcholine liposomes containing incorporated monosialoganglioside

Bovine brain gangliosides incorporated into phospholipid liposomes provide receptors for wheat germ agglutinin. Purified monosialogangliosides were mixed with egg phosphatidylcholine, and unilamellar liposomes were generated. Addition of wheat germ agglutinin induced the liposomes to fuse, and gel filtration analysis revealed that the lectin was incorporated into the fused liposomes. The fusion process was studied by following the changes in the 190° light scattering. Increasing the proportion of the monosialoganglioside in the liposomes was found to increase both the extent of the lectin-induced liposome fusion and the rate of the reaction; below a threshold of approx. 5 mol %, the process was extremely slow. The increase in light scattering could be prevented by the addition of the hapten inhibitor, N- acetyl- d-glucosamine (1 mM). Addition of the inhibitor, subsequent to the lectin, caused a partial decrease in light scattering due to the dissociation of unfused vesicle aggregates. Electron microscopic examination revealed that the ganglioside-containing liposomes were vesicles, 244±25 Å (S.D.) in diameter. Upon addition of wheat germ agglutinin, the vesicles appeared to fuse to form larger vesicles, corresponding to dimers and trimers of the initial vesicles. Inhibition studies with a variety of monosaccharides indicated that the sialic acid moieties present in the gangliosides acted as the lectin-receptor sites. This was confirmed by the observation that wheat germ agglutinin did not interact with phosphatidylcholine vesicles containing desialyated ganglioside.

The interaction of wheat germ agglutinin with keratan from cornea and nasal cartilage

Wheat-germ agglutinin (WGA), a lectin isolated from Trit icum vulgaris, is widely used as a probe for studying carbohydrates found on the surfaces of malignant cells [1,2]. The agglutinin consists of two identical polypeptide chains. Each chain is reported to contain two identical binding sites, which can accomodate a N,N',N-triacetyl chitotriosyl residue [ 1-7] ; internal (l~4)-N-acetyl-fl-D-glucosaminyl residues as well as terminal non-reducing N-acetyl-/3-D-glucosaminyl groups also interact with WGA [5,8,9]. Keratan sulfate, a connective tissue glycosaminoglycan, is composed of six to nine repeating disaccharide units of 4-O-/3-D-galactopyranosyl-N-acetyl-Dglucosamine [10,I 1]; the disaccharide units are glycosidically linked fl, 1-+3 [ 12,13 ]. Each of the carbohydrate residues contains varying amounts:of O-sulfate ester groups at carbon 6. The carbohydrate-binding specificity of WGA suggested that desulfated keratan sulfate should interact with WGA. The present communication documents the specific precipitation of desulfated keratan sulfate with WGA.

Interaction of wheat-germ agglutinin with bacterial cells and cell-wall polymers.

Wheat germ agglutinin was found to agglutinate cells of Escherichia coli PAT 84, Micrococcus luteus, Staphylococcus aureus H, and of S. aureus 52A5, but not cells of S. aureus 52A2. Interaction of wheat germ agglutinin with a soluble linear peptidoglycan secreted by Micrococcus luteus and with the teichoic acid of S. aureus H was demonstrated by agar gel diffusion, quantitative precipitation and inhibition of hemagglutination of trypsinized rabbit erythrocytes. No interaction could be demonstrated with the teichoic acid from a phage-resistant mutant (S. aureus 52A2) which lacks A-acetyl-D-glucosamine residues. All interactions were specifically inhibited by low concentrations of chitotriose (GlcNAcbeta1 leads to 4GlcNAcbeta1 leads to 4GlcNAc) and the bacterial cell wall tetrasaccharide, GlcNAcbeta1 leads to 4MurNAcbeta1 leads to 4GlcNAcbeta1 leads to 4MurNAc. Hemagglutination-inhibition experiments showed that the linear peptidoglycan and the teichoic acid of S. aureus H were several thousand times more potent inhibitors of wheat germ agglutinin than was N-acetyl-D-glucosamine. Comparison of the efficiency of different saccharides in inhibition of hemagglutination and precipitation of polymers by wheat germ agglutinin, strongly suggests that secondary, non-specific interactions contribute to the binding of the lectin to the polymers.

Interaction of wheat germ agglutinin and concanavalin A with isolated fat cells.

Interaction of wheat germ agglutinin and concanavalin A with isolated fat cells.