Lectin structure.

Lectins comprise a structurally very diverse class of proteins characterized by their ability to bind carbohydrates with considerable specificity. They are found in organisms ranging from viruses and plants to humans and serve to mediate biological recognition events. Although lectins bind monosaccharides rather weakly, they employ common strategies for enhancing both the affinity and specificity of their interactions for more complex carbohydrate ligands. The terms subsite and subunit multivalency are defined to describe the ways in which these enhancements are achieved. Analysis of the X-ray crystal structures of different lectin types serves to illustrate how, in structural terms, subsite and subunit multivalency confer context-specific functional properties.