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Iron oxidation in Escherichia coli bacterioferritin ferroxidase centre, a site designed to react rapidly with H2O2 but slowly with O2

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Abstract

Both O2 and H2O2 can oxidize iron at the ferroxidase center (FC) of Escherichia coli bacterioferritin (EcBfr) but mechanistic details of the two reactions need clarification. UV/Vis, EPR, and Mössbauer spectroscopies have been used to follow the reactions when apo‐EcBfr, pre‐loaded anaerobically with Fe2+, was exposed to O2 or H2O2. We show that O2 binds di‐Fe2+ FC reversibly, two Fe2+ ions are oxidized in concert and a H2O2 molecule is formed and released to the solution. This peroxide molecule further oxidizes another di‐Fe2+ FC, at a rate circa 1000 faster than O2, ensuring an overall 1:4 stoichiometry of iron oxidation by O2. Initially formed Fe3+ can further react with H2O2 (producing protein bound radicals) but relaxes within seconds to an H2O2‐unreactive di‐Fe3+ form. The data obtained suggest that the primary role of EcBfr in vivo may be to detoxify H2O2 rather than sequester iron.

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Original languageEnglish
Pages (from-to)8361-8369
Number of pages9
JournalAngewandte Chemie International Edition
Volume60
Issue number15
Early online date22 Jan 2021
DOIs
Publication statusPublished - 6 Apr 2021
Peer-reviewedYes

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