Wheat Germ Agglutinin

Abstract Crystalline wheat germ agglutinin was prepared from unprocessed wheat germ by a new purification procedure. Its purity and some of its molecular characteristics were examined by a number of criteria. Sedimentation analysis gave a molecular weight of 17,000 ± 1,000 and a sedimentation coefficient of 2.1 S when determined in 0.05 n HCl. At neutral pH, the agglutinin dimerizes with a molecular weight of around 35,000 and a sedimentation coefficient of 3.6 S. Amino acid analyses indicate that the protein contains a high amount of glycine and half-cystine; none of the latter is present as cysteine. Three times crystallized agglutinin is devoid of neutral sugars. Equilibrium dialysis experiments using N-acetyl-1-14Cglucosamine indicate that the agglutinin has 2-binding sites for N-acetylglucosamine per mole of the polypeptide chain with a dissociation constant of 7.6 x 10-4 m. This binding is highly specific. The β-1,4 di- and trisaccharides of N-acetylglucosamine showed higher affinities with apparent dissociation constants of 4.9 and 1.2 x 10-5 m, respectively.