Studies on a hemagglutinin from the meadow mushroom. II. Purification, composition, and structure of Agaricus campestris hemagglutinin.

A method is described for the isolation of a phytohemagglutinin from the meadow mushroom, Agaricus campestris. This protein was homogeneous by ultracentrifugation, cellulose acetate electrophoresis, and immunoelectrophoresis. The molecular weight as measured by sedimentation equilibrium was 64,000 and the sedimentation constant, szo,W = 4.8, was independent of protein concentration. There were no disulfide bonds but the hemagglutinin contained 4 “buried” sulfhydryl residues. About 4% of A. campestris hemagglutinin was carbohydrate. In the presence of dissociating solvents such as 6 M guanidine hydrochloride-O.1 M mercaptoethanol and 35 % acetic acid-5 M urea the A. campestris hemagglutinin dissociated. In the guanidine hydrochloride-mercaptoethanol solvent the molecular weight was 16,000 as compared to 64,000 for the native protein. Because this protein contained no disulfide bonds, a noncovalently bonded structure consisting of four polypeptide chains is suggested. In 35% acetic acid-5 M urea, the protein showed two electrophoretic components in equal amounts, suggesting two different subunit types. Tryptic peptide analysis and amino acid composition gave results which were consistent with a molecule consisting of symmetrical halves. A four chain structure of the A& type is proposed for the A. campestris hemagglutinin molecule.