Carboxyl Groups in Carbohydrate-concanavalin a Interaction

I. The role of carboxyl groups in the binding of specific carbohydrates to concanavalin A, the phytohemagglutinin of the jack bean, has been studied using two techniques: (I) H + titration in the presence and absence of methyl a-D-mannopyranoside, a specifically bound carbohydrate ligand and (2) chemical modification of the protein carboxyl groups employing glycine methyl ester and a water-soluble carbodiimide, in the presence and absence of the mannoside. 2. I t is shown that protein carboxyl groups are masked when concanavalin A is t i trated in the presence of the sugar hapten and that this sugar glycoside also protects protein carboxyl groups from modification with glycine methyl ester.