Toxicity of cacmium to Amoeba proteus: a biochemical approach

The cadmium ion (Cd2+) was accumulated by Amoeba proteus in all cellular fractions, the highest level being associated with the cytosol fraction. On gel separation of the cytosol fraction, Cd-binding protein appeared in 2 peaks: one greater than 45,000 MW (PEAK I) and the other 12,000 MW (peak II). Added cysteine increased the total Cd2+ taken up by the cells and resulted in disproportionate increase of Cd incorporated into the Cd-binding protein of peak II. The Cd-binding protein of peak II is analogous to the low-MW, Cd-binding proteins of Anacystis nidulans, Mytilus edulis, and to the metalloprotein of some vertebrates.