Isolation and properties of protein fractions from navy beans (Phaseolus vulgaris) which inhibit growth of rats.

A protein fraction which inhibits growth of weanling rats was obtained from Phaseolus vulgaris seeds of the Sanilac variety by extraction with sodium chloride solution and removal of extraneous materials by precipitation at pH 4.0 and absorption on I : I bentonite-Celite. The protein was precipitated by 0.75 saturation with ammonium sulfate. The growth inhibiting protein fraction contained at least four different proteins separable by electrophoresis, ultracentrifugation, immunodiffusion, and gel chromatography. Only one of the soluble proteins inhibited rat growth, and it comprised about 35 % of the total growth inhibiting fraction and had hemagglutinating activity, stimulated leucocytes, contained very little trypsfl~ inhibitor activity, and had an isoelectric point of pH 5.2 and a mol. wt of approx. IiO ooo. A protein which was insoluble at pH 4 and collected as a precipitate also inhibited growth of rats but because of the small amount isolated and its insolubility, it was not further studied.