X-Ray Crystallographic Studies of Concanavalin A

Abstract

Concanavalin A (Con A), a lectin from the jack bean, Canavalia ensiformis, has a number of unusual properties which promote interest in its three-dimensional structure. More than 50 years ago while working with urease from the same source, Sumner studied some of the other proteins present and thereby isolated, crystallized and named Con A (Sumner, 1919). It agglutinates erythrocytes from various animal species, yeast cells, some bacteria and starch granules (Sumner and Howell, 1936a). Con A has since been shown to precipitate certain glycogens, mucoproteins, dextrans, amylopectins, mannans and blood group substances (Sumner and Howell, 1936b; Goldstein et al., 1965a; Lloyd et al., 1969). Studies of inhibition of Con A-dextran precipitation by various sugars suggest that unmodified hydroxyl groups at the C3, C4, and C6 positions of d-mannopyranose (or d-glucopyranose) are necessary for binding to the active sites of the protein (Goldstein et al., 1965b).