Studies on the interaction of immobilized lectin from Ricinus communis with a simple sugar and a polysaccharide

Abstract

A glycoprotein lectin from Ricinus communis (RCA₁) has been immobilized using concanavalin A. The concanavalin A-immobilized RCA1 retains its sugar binding properties. The number of binding sites (n) and the apparent association constant (K_a) for lactose are not altered on immobilization. This is the first report which indicates that the carbohydrate moieties of a lectin may not be essential for its sugar binding property. The polysaccharide (guar gum) binding can be measured much more effectively by the immobilized RCA₁ as compared to free RCA₁. The pH optimum for the binding of guar gum to RCA₁ is broader for the immobilized RCA₁ as compared to free RCA₁. The immobilized RCA₁ shows considerable stability to thermal inactivation and urea denaturation as compared to free RCA₁. We suggest that the technique of immobilization, where the functional group of a glycoprotein lectin remains available for its biological activity, could prove an important tool for the study of receptor hormone and antibody-antigen interactions.