title: Carbohydrate binding properties of th Dolichos biflorus lectin and its subunits.
abstract: Equilibrium dialysis studies on the binding of the Dolichos biflorus lectin with [14C]methyl alpha-D-GalNAc showed that the lectin has two combining sites/molecule and an intrinsic association constant at 3 degrees C of 4.2 X 10(3) liters mol-1. Binding studies on individual fractions (II, IV, and VII) of the lectin that differ in their chromatographic properties on concanavalin A-Sepharose gave association constants for methyl alpha-D-GalNAc of 2.2 X 10(3) liters mol-1, 3.2 X 10(3) liters mol-1, and 3.2 X 10(3) liters mol-1, respectively. Molecular exclusion chromatography of iodinated Subunits I and II of the lectin, as well as sedimentation velocity studies of the noniodinated subunits, showed that the isolated subunits form aggregates in aqueous solution. Aggregates of subunit I were capable of agglutinating blood type A erythrocytes, precipitating blood group A + H substance, and binding to blood group A + H substance in an affinity electrophoretic system. Aggregates of subunit II exhibited none of these binding properties and did not inhibit the ability of the intact lectin to agglutinate type A erythrocytes. Affinity electrophoresis of subunit I showed that it has an association constant for N-acetyl-D-galactosamine similar to that of the intact lectin. The results suggest that it is subunit I that is primarily responsible for the carbohydrate binding properties of the lectin.
mesh_terms: D000117:Acetylglucosamine / Q000031:analogs & derivatives*; D001789:Blood Group Antigens; D002850:Chromatography, Gel; D005944:Glucosamine / Q000031:analogs & derivatives*; D006386:Hemagglutination Tests; D006801:Humans; D007700:Kinetics; D037102:Lectins; D046911:Macromolecular Substances; D008757:Methylglucosides; D037121:Plant Lectins; D011233:Precipitin Tests; D011485:Protein Binding
chemical_list: D001789:Blood Group Antigens; D037102:Lectins; D046911:Macromolecular Substances; D008757:Methylglucosides; D037121:Plant Lectins; C036554:dolichos biflorus agglutinin; C014088:methyl-2-acetamido-2-deoxy-D-glucopyranoside; D005944:Glucosamine; D000117:Acetylglucosamine