Catalysis of iron core formation in Pyrococcus furiosus ferritin
Catalysis of iron core formation in Pyrococcus furiosus ferritin
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DOI：
10.1007/s00775-009-0571-z
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发表时间：
2009-11-01
影响因子：
3
通讯作者：
Hagen, Wilfred R.
中科院分区：
文献类型：
--
作者：
Ebrahimi, Kourosh Honarmand;Hagedoorn, Peter-Leon;Hagen, Wilfred R.
中空球形的24梅里克铁蛋白可以储存大量的铁作为铁铁矿样矿物核心。在同聚铁蛋白的所有亚基和异聚铁蛋白的催化活性亚基中，发现了通常称为铁氧化酶中心（FC）的二铁结合位点。FC参与蛋白质的催化Fe（II）氧化;然而，不同铁蛋白之间的结构差异可能与铁氧化的不同机制有关。非血红素铁蛋白通常被认为通过所谓的底物FC模型来操作，其中FC通过填充Fe（II）、氧化铁并向空腔提供不稳定的Fe（III）-O-Fe（III）单元来循环。相反，来自大肠杆菌的含血红素的细菌铁蛋白已被提出携带稳定的FC，其通过从氧化Fe（II）的核心的电子转移间接催化Fe（II）氧化。在这里，我们提出了另一种机制的非血红素古菌24梅里克铁蛋白从激烈的热球菌，其中一个稳定的含铁FC作为催化中心的氧化Fe（II），这是随后转移到一个核心，不参与Fe（II）氧化催化。该建议是基于光谱和稳态动力学测量铁氧化和双氧消耗脱铁蛋白和铁蛋白预装不同量的铁。氧化的第一个48 Fe（II）添加到脱铁铁蛋白是光谱和动力学不同，从随后的铁氧化，这被解释为反映FC建设，然后由FC催化的核心形成。
The hollow sphere-shaped 24-meric ferritin can store large amounts of iron as a ferrihydrite-like mineral core. In all subunits of homomeric ferritins and in catalytically active subunits of heteromeric ferritins a diiron binding site is found that is commonly addressed as the ferroxidase center (FC). The FC is involved in the catalytic Fe(II) oxidation by the protein; however, structural differences among different ferritins may be linked to different mechanisms of iron oxidation. Non-heme ferritins are generally believed to operate by the so-called substrate FC model in which the FC cycles by filling with Fe(II), oxidizing the iron, and donating labile Fe(III)-O-Fe(III) units to the cavity. In contrast, the heme-containing bacterial ferritin from Escherichia coli has been proposed to carry a stable FC that indirectly catalyzes Fe(II) oxidation by electron transfer from a core that oxidizes Fe(II). Here, we put forth yet another mechanism for the non-heme archaeal 24-meric ferritin from Pyrococcus furiosus in which a stable iron-containing FC acts as a catalytic center for the oxidation of Fe(II), which is subsequently transferred to a core that is not involved in Fe(II)-oxidation catalysis. The proposal is based on optical spectroscopy and steady-state kinetic measurements of iron oxidation and dioxygen consumption by apoferritin and by ferritin preloaded with different amounts of iron. Oxidation of the first 48 Fe(II) added to apoferritin is spectrally and kinetically different from subsequent iron oxidation and this is interpreted to reflect FC building followed by FC-catalyzed core formation.