Carbohydrate-Binding Specificity of Human Galectins: An Overview by Frontal Affinity Chromatography

To understand the biological functions of lectins, it is important to investigate their sugar-binding specificity. Although galectins are characterized as β-galactoside-binding proteins comprising evolutionarily conserved amino-acid sequences, they have significantly divergent specificities depending on their individual carbohydrate-recognition domains (CRDs). Of the various methods available to analyze lectin-glycan interactions, frontal affinity chromatography is unique in that it provides a quantitative set of dissociation constants (Kd’s) between immobilized lectins and a panel of (>100) fluorescently labeled oligosaccharides. In this article, we provide an overview of the features of galectin specificities with a focus on human galectins based on published data. From the data obtained, comprehensive features of individual CRDs can be systematically understood in terms of branching, and 3′-modifications including sialylation, sulfation, αGal/GalNAc substitutions, β1-3Gal extension, and N-acetyllactosamine repeats. Additionally, we analyze evolutionarily more distant galectin molecules of non-human origins. These findings provide not only basic knowledge but also useful information for their applications: e.g., for engineering superior galectins improved in their specificity and affinity and developing galectin-targeted drugs.