Purification and biochemical characterization of a lysosomal copper-rich thionein-like protein involved in metal detoxification in the digestive gland of mussels

Abstract 1. The lysosomal insoluble Cu-rich protein present in the digestive gland of metal-exposed mussels ( Mytilus galloprovincialis Lam.) was extracted and biochemically characterized. 2. The solubilized Cu-protein shows Chromatographic and electrophoretic properties similar to those of mussel metallothioneins. 3. The UV spectrum of the purified lysosomal Cu-protein is typlcal of Cu-thioneins; it consistently shows an amino acid composition similar to that of previously characterized cytosolic metallothioneins. It differs, however, in that it has a low glycine content as well as a high level of aspartic and glutamic acid. 4. The possible role of lysosomes in metallothionein metabolism is discussed.