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Three Aromatic Residues are Required for Electron Transfer during Iron Mineralization in Bacterioferritin

Bradley, Justin M and Svistunenko, Dimitri A and Lawson, Tamara L and Hemmings, Andrew M and Moore, Geoffrey R and Le Brun, Nick E (2015) 'Three Aromatic Residues are Required for Electron Transfer during Iron Mineralization in Bacterioferritin.' Angewandte Chemie International Edition, 54 (49). pp. 14763-14767. ISSN 1433-7851

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Abstract

Ferritins are iron storage proteins that overcome the problems of toxicity and poor bioavailability of iron by catalyzing 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. Herein, we demonstrate that EcBFR mineralization depends on three aromatic residues near the diiron site, 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. A radical view of bacterioferritin: Three aromatic residues located close to the catalytic ferroxidase site are shown to be important for iron mineralization. A transient radical is associated with Tyr25, consistent with a mechanism where electrons from Fe2+ oxidation are transferred to the oxidized, di-Fe3+ ferroxidase site, ensuring that two electrons arrive at the site simultaneously and avoid formation of toxic reactive oxygen species.

Item Type: Article
Uncontrolled Keywords: bioinorganic chemistry; ferritin; iron; mineralization; tyrosyl radicals
Subjects: Q Science > QD Chemistry
Divisions: Faculty of Science and Health
Faculty of Science and Health > Life Sciences, School of
SWORD Depositor: Elements
Depositing User: Elements
Date Deposited: 28 Jan 2016 16:49
Last Modified: 15 Jan 2022 00:33
URI: http://repository.essex.ac.uk/id/eprint/15992

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