Multiple pathways for mineral core formation in mammalian apoferritin. The role of hydrogen peroxide
Multiple pathways for mineral core formation in mammalian apoferritin. The role of hydrogen peroxide
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DOI：
10.1021/bi027357v
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发表时间：
2003-03-18
期刊：
影响因子：
2.9
通讯作者：
Chasteen, ND
中科院分区：
文献类型：
--
作者：
Zhao, GH;Bou-Abdallah, F;Chasteen, ND
人铁蛋白将铁作为稳定的 FeOOH 矿物质核心隔离并存储在由 H 和 L 两种类型的 24 个亚基组装而成的蛋白质壳内。研究了重组 H 和 L 亚基均聚物和杂聚物铁蛋白以及几种定点 H 亚基变体中的核心矿化，以确定铁氧化/水解化学作为铁流入蛋白质的函数。停流吸收光谱法、紫外光谱法和电极血氧测定法表明，矿物核心至少由三种途径形成，而不是之前认为的两种。它们分别对应于亚铁氧化酶、矿物表面和 Fe(II) + H2O2 解毒反应：2Fe(2+)+O-2+4H(2)O-->2FeOOH((core))+H2O2+4H(+) (1)4Fe(2+)+O-2+6H(2)O-->4FeOOH((core))+8H(+) (2)2Fe(2+)+H2O2+2H(2)O-->2FeOOH((core))+4H(+) (3)H 亚基催化的亚铁氧化酶反应 I 发生在蛋白质铁负载的所有水平上，但随着铁添加量的增加而减少（48-800 Fe(II)/蛋白质）。反应 2 是 800 Fe(11)/蛋白质的主要反应，而反应 3 主要发生在 100-500 Fe(II)/蛋白质的中间铁负载量。反应I中产生的部分H2O2在解毒反应3中被消耗；反应 3 的 2/1 Fe(II)/H2O2 化学计量最大限度地减少了矿化过程中羟基自由基的产生。缺乏功能性成核和/或亚铁氧化酶位点的人 L 链铁蛋白和 H 链变体主要通过矿物质表面反应 2 沉积铁。H2O2 被证明是 L 链以及 H 链和 H 链变体铁蛋白中双氧还原的中间产物。
Human ferritins sequester and store iron as a stable FeOOH(s) mineral core within a protein shell assembled from 24 subunits of two types, H and L. Core mineralization in recombinant H- and L-subunit homopolymer and heteropolymer ferritins and several site-directed H-subunit variants was investigated to determine the iron oxidation/hydrolysis chemistry as a function of iron flux into the protein. Stopped-flow absorption spectrometry, UV spectrometry, and electrode oximetry revealed that the mineral core forms by at least three pathways, not two as previously thought. They correspond to the ferroxidase, mineral surface, and the Fe(II) + H2O2 detoxification reactions, respectively:2Fe(2+)+O-2+4H(2)O-->2FeOOH((core))+H2O2+4H(+) (1)4Fe(2+)+O-2+6H(2)O-->4FeOOH((core))+8H(+) (2)2Fe(2+)+H2O2+2H(2)O-->2FeOOH((core))+4H(+) (3)The H-subunit catalyzed ferroxidase reaction I occurs at all levels of iron loading of the protein but decreases with increasing iron added (48-800 Fe(II)/protein). Reaction 2 is the dominant reaction at 800 Fe(11)/protein, whereas reaction 3 occurs largely at intermediate iron loadings of 100-500 Fe(II)/protein. Some of the H2O2 produced in reaction I is consumed in the detoxification reaction 3; the 2/1 Fe(II)/H2O2 stoichiometry of reaction 3 minimizes hydroxyl radical production during mineralization. Human L-chain ferritin and H-chain variants lacking functional nucleation and/or ferroxidase sites deposit their iron largely through the mineral surface reaction 2. H2O2 is shown to be an intermediate product of dioxygen reduction in L-chain as well as in H-chain and H-chain variant ferritins.