School of Life Sciences, University of Essex, Wivenhoe Park, Colchester, Essex, CO4 3SQ, UK.
Université Grenoble Alpes, CNRS, CEA, IRIG, Laboratoire de Chimie et Biologie des Métaux, UMR 5249, 17 rue des Martyrs, 38000, Grenoble, France.
Angew Chem Int Ed Engl. 2021 Apr 6;60(15):8361-8369. doi: 10.1002/anie.202015964.
Both O and H O 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 Fe , was exposed to O or H O . We show that O binds di-Fe FC reversibly, two Fe ions are oxidized in concert and a H O molecule is formed and released to the solution. This peroxide molecule further oxidizes another di-Fe FC, at a rate circa 1000 faster than O , ensuring an overall 1:4 stoichiometry of iron oxidation by O . Initially formed Fe can further react with H O (producing protein bound radicals) but relaxes within seconds to an H O -unreactive di-Fe form. The data obtained suggest that the primary role of EcBfr in vivo may be to detoxify H O rather than sequester iron.
O 和 H O 均可氧化大肠杆菌菌铁蛋白（EcBfr）的亚铁氧化酶中心（FC），但两种反应的具体机制仍需阐明。我们采用紫外/可见分光光度法、电子顺磁共振波谱法和穆斯堡尔谱法，跟踪研究了去铁 apo-EcBfr 在无氧条件下预先加载 Fe 后，与 O 或 H O 反应的过程。结果表明，O 可与二价铁 FC 可逆结合，两个 Fe 离子同时被氧化，同时形成一个 H O 分子并释放到溶液中。该过氧化物分子进一步氧化另一个二价铁 FC，其速率比 O 快约 1000 倍，从而确保 O 以 1:4 的化学计量比氧化铁。最初形成的 Fe 可以进一步与 H O 反应（产生蛋白结合自由基），但几秒钟内即可弛豫到 H O 不反应的二价铁形式。所得数据表明，EcBfr 在体内的主要作用可能是解毒 H O 而不是螯合铁。
