Redox Reactivity of Bacterial and Mammalian Ferritin: Is Reductant Entry Into the Ferritin Interior a Necessary Step for Iron Release?

Author Info

G. D. Watt, University of Colorado
D. Jacobs, Battelle-C. F. Kettering Research Laboratory
Richard B. Frankel, California Polytechnic State University - San Luis ObispoFollow

Recommended Citation

Postprint version. Published in Proceedings of the National Academy of Science of the United States of America, Volume 85, Issue 20, October 15, 1988, pages 7457-7461.

Abstract

Both mammalian and bacterial ferritin undergo rapid reaction with small-molecule reductants, in the absence of Fe²⁺ chelators, to form ferritins with reduced (Fe²⁺) mineral cores. Large, low-potential reductants (flavoproteins and ferredoxins) similarly react anaerobically with both ferritin types to quantitatively produce Fe²⁺ in the ferritin cores. The oxidation of Fe²⁺ ferritin by large protein oxidants [cytochrome c and Cu(II) proteins] also occurs readily, yielding reduced heme and Cu(I) proteins and ferritins with Fe³⁺ in their cores. These latter oxidants also convert enthetically added Fe²⁺, bound in mammalian or bacterial apo- or holo-ferritin, to the corresponding Fe³⁺ state in the core of each ferritin type. Because the protein reductants and oxidants are much larger than the channels leading into the mineral core attached to the ferritin interior, we conclude that redox reactions involving the Fe²⁺/Fe³⁺> components of the ferritin core can occur without direct interaction of the redox reagent at the mineral core surface. Our results also suggest that the oxo, hydroxy species of the core, composed essentially of Fe(O)OH, arise exclusively from solvent deprotonation. The long-distance ferritin-protein electron transfer observed in this study may occur by electron tunneling.

Disciplines

Physics

Copyright

1988 National Academy of Sciences.

Publisher statement

The original publication is available at http://www.pnas.org/content/85/20/7457.abstract.