A Comparative Evaluation of the Level of Concanavalin A Binding by Enriched Plasma Membrane Fractions From Developing Soybean Roots

The Concanavalin A (Con A) binding capacity of plasma membranes isolated from meristematic and mature regions of four-day-old soybean (Glycine max L. Merr. cv. Wells) roots was compared. Con A binding was studied using a radiochemical assay with tritiated ((3)H)-Con A and by an electron microscope technique using Con A-ferritin (Con A-F). In both cases, plasma membranes isolated from meristematic tissue bound significantly more Con A than did corresponding membranes from mature tissue. The relative difference in reactivity, as determined by the two procedures, was approximately 49% ((3)H-Con A) and 46% (Con A-F). In contrast, K(m) values, determined from (3)H-Con A binding curves, were approximately the same, indicating that receptor sites on plasma membranes from both sources were qualitatively similar.Since Con A specifically interacts with saccharide-containing portions of membrane glycoproteins and/or glycolipids, the data suggests that there is a decrease in the concentration of those components in plasma membranes during development or that there are qualitative changes in the structure of their oligosaccharide side chains.