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Bradley, Justin M., Svistunenko, Dimitri A., Lawson, Tamara L., Hemmings, Andrew M., Moore, Geoffrey R. and Le Brun, Nick E. 
ORCID: https://orcid.org/0000-0001-9780-4061
(2015)
Three aromatic residues are required for electron transfer during iron mineralization in Bacterioferritin.
Angewandte Chemie-International Edition, 127 (49).
14976–14980.
ISSN 1433-7851
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Abstract
Ferritins are iron storage proteins that overcome problems of toxicity and poor bioavailability of iron by catalysing iron oxidation and mineralization through the activity of a diiron ferroxidase site. Unlike in other ferritins, the oxidized di-Fe3+ site of Escherichia coli bacterioferritin (EcBFR) is stable and therefore does not function as a conduit for the transfer of Fe3+ into the storage cavity, but instead acts as a true catalytic cofactor that cycles its oxidation state while driving Fe2+ oxidation in the cavity. Here we demonstrate that EcBFR mineralization depends on three near-diiron site aromatic residues, Tyr25, Tyr58 and Trp133, and that a transient radical is formed on Tyr25. The data indicate that the aromatic residues, together with a previously identified inner surface iron site, promote mineralization by ensuring the simultaneous delivery of two electrons, derived from Fe2+ oxidation in the BFR cavity, to the di-ferric catalytic site for safe reduction of O2.
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