Isolation and chemical characterization of a highly purified phytomitogen from Phaseolus coccineus seeds.

An effective lymphocyte mitogen with a low erythroagglutinating ability was isolated from the seeds of Phaseolus coccineus L. by ammonium sulphate precipitation and repeated ion-exchange chromatography on modified Sephadex. The mitogen stimulated lymphocytes at concentrations as low as 0.25 microgram/ml, the optimum concentration being in the range of 2.5-5.0 microgram/ml. This stimulating effect was completely inhibited by 5 mg/ml methyl alpha-D-mannopyranoside. Column gel filtration, disc electrophoresis on polyaceylamide gel in an alkaline medium and in the presence of sodium dodecylsulphate and the finding of a single N-terminal amino acid (alanine) showed the phytomitogen to be homogenous. Disc electrophoresis in an acid medium revealed the presence of two or three bands which are assumed to be due to aggregates of the mitogen. The minimum molecular weight, as derived from sodium dodecylsulphate electrophoresis on polyacrylamide, was 35000. The mitogen is a glycoprotein containing 10% neutral sugars and 1.3% amino sugars (glucosamine). The amino acid composition of the isolated phytomitogen is presented.