Erythrocyte-binding studies on an acidic lectin from winged bean (Psophocarpus tetragonolobus)

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Abstract
An acidic lectin (WBA II) was isolated to homogeneity from the crude seed extract of the winged bean (Psophocarpus tetragonolobus) by affinity chromatography on lactosylaminoethyl-Bio-Gel. Binding of WBA II to human erythrocytes of type-A, -B and -O blood groups showed the presence of 105 receptors/cell, with high association constants (106-108 m-1). Competitive binding studies with blood-group-specific lectins reveal that WBA II binds to H- and T-antigenic determinants on human erythrocytes. Affinity-chromatographic studies using A-, B-, H-, and T-antigenic coupled to an insoluble matrix confirm the specificity of WBA II towards H- and T-antigenic determinants. Inhibition of the binding of WBA II by various sugars show that N-acetylgalactosamine and T-antigenic disaccharide (Thomsen-Friedenreich antigen, Gal.beta.1-3GalNAc) are the most potent mono-and di-saccharide inhibitors respectively. In addition, inhibition of the binding of WBA II to erythrocytes by dog intestine H-fucolipid prove that the lectin binds to H-antigentic determinant.