Identification of extracellular haemoglobin as the major high molecular weight cadmium-binding protein of the polychaete annelid Nereis diversicolor

Abstract

Abstract 1. A high molecular weight cadmium-binding protein called MP I was isolated from Nereis diversicolor exposed to 20 ppm of cadmium (CdCl 2 ) for 4 days via sea water. 2. The protein had a molecular weight comprising between 20 × 10 6 and 1.5 × 10 6 Da. It shows high absorptions at 280 and 415 nm and contained iron in addition to cadmium. 3. Two dimensional SDS-PAGE of unreduced and reduced MP I revealed a dissociation pattern similar to that of extracellular haemoglobins of polychaetes and oligochaetes. 4. Furthermore, negatively stained MP I molecules examined by conventional transmission electron microscopy showed the common appearance of extracellular haemoglobins of annelids. 5. Evidence of the extracellular haemoglobin nature for the MP I was found by the identical Chromatographie behaviour of MP I with the main Nereis blood component and, by the labelling of blood vessel content with 109 Cd visualized by autoradiography on paraffin-embedded sections of exposed Nereis .