Functional and mutational characterization of human MIA40 acting during import into the mitochondrial intermembrane space
Functional and mutational characterization of human MIA40 acting during import into the mitochondrial intermembrane space
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DOI：
10.1016/j.jmb.2005.08.064
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发表时间：
2005-10-28
影响因子：
5.6
通讯作者：
Bauer, MF
中科院分区：
文献类型：
--
作者：
Hofmann, S;Rothbauer, U;Bauer, MF
最近在酵母中描述了第一种参与输入线粒体膜间隙的组分，命名为Mia 40。在这里，我们确定了人类MIA 40作为一种新的和普遍表达的人类线粒体的组成部分。它属于一个新的蛋白质家族，其成员共享六个高度保守的半胱氨酸残基，构成-CXC-CX 9 C-CX 9 C-基序。人MIA 40明显小于真菌蛋白，并且缺乏包括跨膜区和线粒体靶向信号的N-末端延伸。它在人线粒体的膜间隙内形成可溶性复合物。通过RNA干扰消除人类细胞中的MIA 40特异性地影响小的和含半胱氨酸的膜间空间蛋白如DDP 1和TIM 10 A的稳态水平，这表明MIA 40沿着进入膜间空间的输入途径起作用。对人MIA 40的体内氧化还原状态的研究表明，它含有分子内二硫键。巯基捕获分析揭示了细胞内不同氧化态的人MIA 40的共存。此外，我们表明，双-CX 9 C-基序是特别需要的进口和稳定的MIA 40在线粒体。该基序的部分突变影响MIA 40在膜间隙中的稳定积累，而该基序中的所有半胱氨酸残基的突变抑制线粒体中的输入。两者合计，我们得出结论，MIA 40在线粒体膜间隙的生物起源和功能是依赖于氧化还原过程，涉及保守的半胱氨酸残基。(c)2005爱思唯尔有限公司保留所有权利。
A first component involved in import into the mitochondrial intermembrane space, named Mia40, has been described recently in yeast. Here, we identified the human MIA40 as a novel and ubiquitously expressed component of human mitochondria. It belongs to a novel protein family whose members share six highly conserved cysteine residues constituting a -CXC-CX9C-CX9C- motif. Human MIA40 is significantly smaller than the fungal protein and lacks the N-terminal extension including a transmembrane region and mitochondrial targeting signal. It forms soluble complexes within the intermembrane space of human mitochondria. Depletion of MIA40 in human cells by RNA interference specifically affected steady-state levels of small and cysteine-containing intermembrane space proteins like DDP1 and TIM10A, suggesting that MIA40 acts along the import pathway into the intermembrane space. Studies on the in vivo redox state of human MIA40 demonstrated that it contains intramolecular disulfide bonds. Thiol-trapping assays revealed the co-existence of different oxidation states of human MIA40 within the cell. Furthermore, we show that the twin -CX9C- motif is specifically required for import and stability of MIA40 in mitochondria. Partial mutation of this motif affects stable accumulation of MIA40 in the intermembrane space, whereas mutation of all cysteine residues in this motif inhibits import in mitochondria. Taken together, we conclude that the biogenesis and function of MIA40 in the mitochondrial intermembrane space is dependent on redox processes involving conserved cysteine residues. (c) 2005 Elsevier Ltd. All rights reserved.