Iron Oxidation in Escherichia coli Bacterioferritin Ferroxidase Centre, a Site Designed to React Rapidly with H2O2 but Slowly with O$_2$

Jacob Pullin (1) , Wilson Michael T. (1) , Martin Clémancey (2) , Geneviève Blondin (2) , Justin M. Bradley (3) , Geoffrey R. Moore (3) , Nick E. Le Brun (3) , Marina Lučić (1) , Jonathan A. Worrall (1) , Dimitri A. Svistunenko (1)

1 University of Essex
2 PMB - Physiochimie des Métaux
3 UEA - University of East Anglia [Norwich]

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.

Mots clés: EPR spectroscopy; fast kinetics; ferroxidase center; Mossbauer spectroscopy; rapid freeze-quenching

Domaines: Biochimie [q-bio.BM]; Bactériologie

Jacob Pullin, Wilson Michael T., Martin Clémancey, Geneviève Blondin, Justin M. Bradley, et al.. Iron Oxidation in Escherichia coli Bacterioferritin Ferroxidase Centre, a Site Designed to React Rapidly with H2O2 but Slowly with O$_2$. Angewandte Chemie International Edition, 2021, 60 (15), pp.8361-8369. ⟨10.1002/anie.202015964⟩. ⟨hal-03191972⟩