Pure Canavalia ensiformis lectin (Con A) from Jackbean. Isolated by affinity chromatography on cross-linked dextran. Con A exists as a dimer below pH 5.0 and and at pH >7 it exists as a tetramer. Con-A is not a glycoprotein. The monomeric molecular weight of Con-A is 25,500. Con-A does not contain cysteine residues. Unlike most other lectins, Con-A is a metalloprotein and requires a transition metal ion, such as manganese, plus calcium ions for binding. Lectins are proteins or glycoproteins of non-immune origin that agglutinate cells and/or precipitate complex carbohydrates. Lectins are capable of binding glycoproteins even in presence of various detergents. The agglutination activity of these highly specific carbohydrate-binding molecules is usually inhibited by a simple monosaccharide, but for some lectins, di, tri, and even polysaccharides are required.