Key carboxylate residues for iron transit through the prokaryotic ferritin SynFtn.
Key carboxylate residues for iron transit through the prokaryotic ferritin SynFtn.
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DOI：
10.1099/mic.0.001105
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发表时间：
2021-11
期刊：
影响因子：
--
通讯作者：
Le Brun NE
中科院分区：
文献类型：
--
作者：
Bradley JM;Fair J;Hemmings AM;Le Brun NE
铁蛋白是一种形成24 - meric菱形十二面体笼的蛋白质，在所有细胞类型的铁储存和解毒中起关键作用。它们的功能需要将Fe2+从蛋白质的外部运输到被称为铁氧化酶中心的埋藏的二铁催化位点，在那里，Fe2+被氧化形成铁蛋白矿物核心的Fe3+-氧前体。铁通过动物铁蛋白的转运途径已经被很好地理解：铁离子底物通过三轴通道进入蛋白质，蛋白质笼内表面的保守羧酸盐已被证明有助于形成瞬时结合位点，将铁离子引导到铁氧化酶中心。铁通过原核铁蛋白的运输途径研究较少，但至少对一些人来说，有证据表明双轴通道是铁离子摄取的主要途径。SynFtn是从蓝细菌聚球菌CC9311中分离出来的，是一种非典型的原核铁蛋白，最近被证明通过其三重通道吸收Fe2+。然而，动物铁蛋白中保守的转移位点羧酸残基缺失，这意味着从铁进入SynFtn的位点到催化中心的路线尚未确定。在这里，我们报告了使用位点定向诱变，吸收监测活性测定和蛋白质晶体学的组合来探测替代可能参与该途径的两个残基的影响。Glu141和Asp65都在引导Fe2+底物到达氧化铁酶中心的过程中发挥作用。在缺乏Asp65的情况下，Fe2+进入和Fe3+从氧化铁酶中心流出的路线受到影响，导致矿物岩心的低效形成。这些观察结果进一步确定了铁转运路线，这可能是蓝藻特有的一类新的铁蛋白的第一个特征例子。
Ferritins are proteins forming 24meric rhombic dodecahedral cages that play a key role in iron storage and detoxification in all cell types. Their function requires the transport of Fe2+ from the exterior of the protein to buried di-iron catalytic sites, known as ferroxidase centres, where Fe2+ is oxidized to form Fe3+-oxo precursors of the ferritin mineral core. The route of iron transit through animal ferritins is well understood: the Fe2+ substrate enters the protein via channels at the threefold axes and conserved carboxylates on the inner surface of the protein cage have been shown to contribute to transient binding sites that guide Fe2+ to the ferroxidase centres. The routes of iron transit through prokaryotic ferritins are less well studied but for some, at least, there is evidence that channels at the twofold axes are the major route for Fe2+ uptake. SynFtn, isolated from the cyanobacterium Synechococcus CC9311, is an atypical prokaryotic ferritin that was recently shown to take up Fe2+ via its threefold channels. However, the transfer site carboxylate residues conserved in animal ferritins are absent, meaning that the route taken from the site of iron entry into SynFtn to the catalytic centre is yet to be defined. Here, we report the use of a combination of site-directed mutagenesis, absorbance-monitored activity assays and protein crystallography to probe the effect of substitution of two residues potentially involved in this pathway. Both Glu141 and Asp65 play a role in guiding the Fe2+ substrate to the ferroxidase centre. In the absence of Asp65, routes for Fe2+ to, and Fe3+ exit from, the ferroxidase centre are affected resulting in inefficient formation of the mineral core. These observations further define the iron transit route in what may be the first characterized example of a new class of ferritins peculiar to cyanobacteria.
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影响因子：
2.9
作者：
Bou-Abdallah, F.;Yang, H.;Awomolo, A.;Cooper, B.;Woodhall, M. R.;Andrews, S. C.;Chasteen, N. D.
通讯作者：
Chasteen, N. D.
影响因子：
3.4
作者：
Bradley, Justin M.;Svistunenko, Dimitri A.;Le Brun, Nick E.
通讯作者：
Le Brun, Nick E.
影响因子：
14.8
作者：
Ebrahimi, Kourosh Honarmand;Bill, Eckhard;Hagen, Wilfred R.
通讯作者：
Hagen, Wilfred R.
影响因子：
4.3
作者：
Ciambellotti, Silvia;Pozzi, Cecilia;Turano, Paola
通讯作者：
Turano, Paola
DOI：
10.1107/s0907444910007493
发表时间：
2010-04
期刊：
Acta crystallographica. Section D, Biological crystallography
影响因子：
--
作者：
Emsley P;Lohkamp B;Scott WG;Cowtan K
通讯作者：
Cowtan K