Ferritin polymers and the formation of haemosiderin.

When ferritin is isolated from Chang liver cells in culture iron loading is found to be associated with changes in the surface of the protein shell characterized by a change in immunoreactivity to anti "heart' and anti"spleen' antibodies at each specific pI and an overall shift in isoferritins to a lower pI range (Hoy & Jacobs, 1981). Ferritin polymers have been isolated from human tissues and their biochemical properties assessed in terms of these surface changes and the iron/protein ratio of the molecules. The results suggest that changes in the surface of ferritin molecules are associated with the formation of stable polymers. These are precursors of clumps of ferritin and eventually haemosiderin. Changes in the surface of the molecule may provide a signal for polymerization and incorporation of the protein within the lysosomes.