Isolation and characterization of ferritin from the hepatopancreas of the musselMytilus edulis

Abstract

The main iron-binding protein in the hepatopancreas of the mussel Mytilus edulis, which had been previously iron-loaded by exposure to carbonyl iron (spheres of elemental iron less than 5 μm diameter), has been isolated to electrophoretic purity and identified as ferritin. This ferritin has Mr, of 480000, pI of 4.7-5.0 and is composed of two subunits, Mr 18500 and Mr 24600. Under the electron microscope, it appears as electron-dense iron cores of average diameter 5 nm surrounded by a polypeptide shell to a final average overall diameter of 11 nm. The purified protein contains, on average, 200 iron atoms/molecule protein. On immunodiffusion, M. edulis hepatopancreas ferritin gives a partial cross-reaction with antiserum to horse spleen ferritin and lamprey (Geotria australis) liver ferritin but does not react with antiserum to chiton (Acanthopleura hirtosa) haemolymph ferritin.