Cadmium-binding proteins in the scallop Pecten maximus.

Scallops, Pecten maximus, accumulate cadmium naturally in the digestive gland to a level of approximately 100 ppm wet weight. Of this cadmium, 60% was soluble and was composed of three weight classes as judged by Sephadex G-100 chromatography. Of the soluble cadmium, 60% was in the 55,000 molecular weight range and 20% each in an excluded fraction and a 10,000 molecular weight fraction. The 55,000 molecular weight fraction, after further purification, showed a maximum cadmium concentration of 1.4% by weight. The cadmium was thiolate bound but not as strongly bound as in the case of metallothionein. The 10,000 molecular weight fraction was a metallothionein-like protein.