Protein-Carbohydrate Interaction III. Agar Gel-Diffusion Studies on the Interaction of Concanavalin A, a Lectin Isolated from Jack Bean, with Polysaccharidesl

Concanavalin A, a protein isolated from the jack bean (Canavalia ensijormis), has previously been shown to form a precipitate with glycogen and yeast mannan, and more recently with dextrans and amylopectin. Double-diffusion precipitation studies in agar gel have been found to afford a very sensitive and satisfactory method for investigating the interaction of concanavalin A with certain types of branched, glucoseand mannosecontaining polysaccharides. In this manner concanavalin A can be used as a reagent for the detection and preliminary characterization of various types of polysaccharides. Bacterial levans as well as certain plant fructans also form precipitation bands with concanavalin A. This observation represents the first report of such an interaction. The method may also provide an indication as to the heterogeneity of polysaccharide preparations that react with concanavalin A as well as affording preliminary information on the relative molecular size of a series of reactive polysaccharides. Inhibition of the precipitation bands by low molecular weight carbohydrate molecules may be demonstrated. These inhibition studies reveal the highly specific nature of the combining sites of the concanavalin A molecule.