Purification and characterization of metal-binding proteins from the digestive gland of the Japanese scallop Mizuhopecten yessoensis.

Marine bivalves accumulate high concentrations of potentially toxic heavy metals in their tissues. We report here our investigation of the accumulation patterns of cadmium (Cd), copper (Cu), and lead (Pb) in tissues of the Japanese scallop Mizuhopecten yessoensis after exposure to artificial seawater containing Cd, Cu, or Pb. Our results revealed that accumulation of these heavy metals by this scallop was associated with certain intracellular metal-binding proteins (MBPs). Cd was accumulated at higher concentrations than Cu and Pb, and most of the accumulated metals were detected in the digestive gland. MBPs from the digestive gland were purified and subjected to a preliminary characterization. Three proteins with molecular masses of approximately 28, 37, and 42 kDa, respectively, were isolated by gel-filtration and anion-exchange column chromatography. Characterization of the partial amino acid sequences of these proteins show high sequence similarity to MBPs and ion-transporters. Metalloprotein profiles in the digestive gland indicated that some proteins were upregulated after metal exposure, suggesting that these proteins are involved in mechanisms of metal accumulation and detoxification in M. yessoensis. [ABSTRACT FROM AUTHOR]