Isolation of four isotoxic proteins and one agglutinin from jequiriti bean ( Abrus precatorius)

Abstract

Four isotoxic proteins and one agglutinin were purified from the seeds of Abrus precatorius by Sepharose 4B and DEAE-cellulose column chromatography. Abrin-b and abrin-c which bind weakly on the Sepharose 4B are eluted from the column in the absence of galactose while abrin-a, abrin-d and abrus agglutinin which bind strongly are eluted with 0·1M galactose. The mol. wts of abrin-a and abrin-c are 63,000 and abrin-b, abrin-d and abrus agglutinin 67,000. The lethality of the four abrins was similar; 10, 25, 16 and 31 μg/kg body wt for abrin-a, b, c and d, respectively. The amino acid compositions of four isotoxic proteins and the A and B subunit of three isotoxic proteins are similar but not identical, and they are different from those of abrus agglutinin.