Characterisation of cadmium-binding proteins from mussels, Mytilus edulis (L), exposed to cadmium.

Three Cd2+-binding proteins have been purified and partially characterised from the digestive gland of the bivalve mollusc, Mytilus edulis, after exposure to Cd2+. The major protein, which was judged to be pure on polyacrylamide gel electrophoresis, showed many of the characteristics of mammalian metallothionein; having a high -SH content, few aromatic amino acids and a high A250/A280 nm ratio which disappears on acidification. It also contains Zn and Cu, but differs in its higher apparent molecular weight of about 25 000 and high glycine content (12-19%). The two additional Cd2+-binding proteins had lower cysteine contents and different molar proportions of Cd2+, Zn2+ and Cu2+.