Lectins: To Combat Infections

The term “lectin” was coined by William Boyd in 1954 from the Greek word “legere” which means “to select” or “to bind”. Lectins and hemagglutinins are proteins/glycoproteins of non-immune origin, which have at least one non-catalytic domain that exhibits reversible binding to specific monosaccharides or oligosaccharides (Lis and Sharon, 1986). The lectinmonosaccharide interactions are relatively very weak and the dissociation constants lie in millimolar range. However, in nature for the multimeric sugars the dissociation constants are several folds higher indicating that multiple protein-carbohyrate interactions are involved in the recognition and binding events (Ambrosi et al., 2005). Thus, lectins are multivalent in nature and can bind to the carbohydrate moieties on the surface of erythrocytes and agglutinate the erythrocytes, without altering the properties of the carbohydrates (Lam and Ng, 2011). Lectins are ubiquitous and are extensively distributed in nature. Many hundreds of these lectins have been isolated from varied sources like plants, viruses, bacteria, invertebrates and vertebrates but in all, lectins from different sources show little similarity. Lectins are invaluable tools for the detection, isolation, and characterization of glycoconjugates, primarily of glycoproteins, for histochemistry of cells and tissues and for the examination of changes that occur on cell surfaces during physiological and pathological processes, from cell differentiation to cancer (Sharon and Lis, 2004).