Department of Biochemical Sciences "A. Rossi-Fanelli", Sapienza University of Rome, P.le Aldo Moro 5, 00185 Rome, Italy.
INSTM, Department of Chemistry "U. Schiff", University of Florence, Via della Lastruccia, 3-13 50019 Sesto Fiorentino, Florence, Italy.
J Inorg Biochem. 2018 May;182:103-112. doi: 10.1016/j.jinorgbio.2018.02.003. Epub 2018 Feb 9.
Ferritins are ubiquitous and conserved proteins endowed with enzymatic ferroxidase activity, that oxidize Fe(II) ions at the dimetal ferroxidase centre to form a mineralized Fe(III) oxide core deposited within the apo-protein shell. Herein, the in vitro formation of a heterodimetal cofactor constituted by Fe and Mn ions has been investigated in human H ferritin (hHFt). Namely, Mn and Fe binding at the hHFt ferroxidase centre and its effects on Fe(II) oxidation have been investigated by UV-Vis ferroxidation kinetics, fluorimetric titrations, multifrequency EPR, and preliminary Mössbauer spectroscopy. Our results show that in hHFt, both Fe(II) and Mn(II) bind the ferroxidase centre forming a Fe-Mn cofactor. Moreover, molecular oxygen seems to favour Mn(II) binding and increases the ferroxidation activity of the Mn-loaded protein. The data suggest that Mn influences the Fe binding and the efficiency of the ferroxidation reaction. The higher efficiency of the Mn-Fe heterometallic centre may have a physiological relevance in specific cell types (i.e. glia cells), where the concentration of Mn is the same order of magnitude as iron.
铁蛋白是普遍存在且保守的蛋白质，具有酶促亚铁氧化酶活性，可将二价铁离子氧化为双金属亚铁氧化酶中心的矿化 Fe(III) 氧化物核心，沉积在脱辅基蛋白壳内。本文研究了人 H 铁蛋白 (hHFt) 中由 Fe 和 Mn 离子组成的杂二金属辅因子的体外形成。具体而言，通过紫外可见亚铁氧化动力学、荧光滴定、多频 EPR 和初步穆斯堡尔光谱研究了 Mn 和 Fe 在 hHFt 亚铁氧化酶中心的结合及其对 Fe(II)氧化的影响。结果表明，在 hHFt 中，Fe(II)和 Mn(II)都结合亚铁氧化酶中心形成 Fe-Mn 辅因子。此外，分子氧似乎有利于 Mn(II)结合并增加负载 Mn 的蛋白质的亚铁氧化活性。数据表明，Mn 影响 Fe 的结合和亚铁氧化反应的效率。Mn-Fe 杂金属中心的更高效率可能在特定细胞类型（如神经胶质细胞）中具有生理相关性，其中 Mn 的浓度与铁处于同一数量级。
