[2][3] The exact function of the legume lectins in vivo is unknown but they are probably involved in the defense of plants against predators.

They have been used for decades as a model system for the study of protein-carbohydrate interactions, because they show a wide variety of binding specificities and are easy to obtain, purify, and characterize the structure of.

[3] Well-studied members of this protein family include phytohemagglutinin, soybean agglutinins, and concanavalin A.

The legume lectins use an ingenious framework for binding specific sugars.

This framework consists of a conserved monosaccharide binding site in which four conserved residues from four separate regions in the protein confer affinity (see figure), a variable loop that confers monosaccharide specificity and a number of subsites around the monosaccharide binding site that harbour additional sugar residues or hydrophobic groups.