Role of metallothioneins in disease.

Metallothioneins are small proteins (6,000 to 10,000 mw) with similar amino acid compositions, high content of sulfhydryl amino acids and no aromatic amino acids. Emax at 250 nm is due to cadmium mercaptide bond. Synthesis is induced by a number of metals including zinc, cadmium, mercury, copper, bismuth, gold and silver. These proteins function as a mechanism of intracellular storage of some essential metals such as zinc and copper. Binding of potentially toxic metals like cadmium may be protective; but with saturation of protein by metal, toxicity may occur. Excessive cadmium-thionein may have a role in the pathogenesis of cadmium induced kidney disease. A more sensitive method for detection adn measurement of this protein will greatly enhance future studies, particularly the potential for clinical application.