Characterization of Cadmium-Binding Complexes from the Roots of Cadmium-Treated Rice Plant

Cadmium-binding complexes were isolated from the roots of cadmium-treated rice plant. Extractant was chromatographed on a Sephadex G-50 column and the fractions, rich in SH group and cadmium, were purified further by chromatography on DEAE-Sephadex A-25. The resulting complex preparation had an apparent molecular weight of 5,600, contained 44% cysteine and 39% glutamate and lacked in aromatic amino acids. The cadmium: cysteine ratio was 1 : 2. Spectroscopic measurements indicated the presence of a cadmium-mercaptide bonding. The rice roots produced metallothionein-like substances when they were exposed to cadmium.