The purification and characterization of wheat-germ agglutinin

Abstract

The purification of wheat-germ agglutinin by precipitation with ammonium sulphate and by chromatography on Sephadex G-75, Sepharose–ovomucoid and CM-cellulose is described. This procedure gave agglutinin preparations which were homogeneous on polyacrylamide gels under a variety of conditions. Purified wheat-germ agglutinin formed colourless solutions and was relatively insoluble at neutral pH; maximum solubility in 1mm-tris–HCl buffer, pH7.4, was approx. 1mg/ml. The agglutinin was a glycoprotein containing a single polypeptide chain with an approximate molecular weight of 23000. The N-terminus of the oxidized agglutinin was cysteic acid and the C-terminus was glycine. The amino acid composition showed that the protein was extremely rich in cysteine and cystine; there were 15–17 free SH groups/mol. The absorption maximum for the protein was at 272nm and the molar extinction coefficient at 280nm was 1.09×105 litre·mol-1·cm-1. Equilibrium dialysis indicated that there was only one binding site per molecule for N-acetylglucosamine.