The formation of ferritin from apoferritin. Inhibition and metal ion-binding studies

Abstract

Inhibition by Zn2+of iron uptake by apoferritin at very low substrate concentrations is shown to be competitive. It is proposed that Zn2+competes with Fe2+for sites on the protein at which the oxidation of Fe2+is catalysed. Interpretation of titration data suggests there are two independent classes of binding site for Zn2+and several other cations. Sites in one such class are probably on the external surface of the apoferritin molecule. The catalytic binding sites are presumed to be internal and may involve histidine or possibly cysteine as ligands.