Magnetic Resonance Center (CERM), University of Florence , Via Luigi Sacconi 6, 50019 Sesto Fiorentino, Florence, Italy.
Department of Chemistry, University of Florence , Via della Lastruccia 3, 50019 Sesto Fiorentino, Florence, Italy.
J Am Chem Soc. 2017 Jul 19;139(28):9479-9482. doi: 10.1021/jacs.7b05003. Epub 2017 Jul 6.
Human mitoNEET is a homodimeric protein anchored to the outer mitochondrial membrane and has a C-terminal [2Fe-2S] binding domain located in the cytosol. Recently, human mitoNEET has been shown to be implicated in Fe/S cluster repair of cytosolic iron regulatory protein 1 (IRP1), a key regulator of cellular iron homeostasis in mammalian cells. The Fe/S cluster repair function of mitoNEET is based on an Fe/S redox switch mechanism: under normal cellular conditions, reduced [2Fe-2S]-mitoNEET is present and is inactive as an Fe/S cluster transfer protein; under conditions of oxidative cellular stress, the clusters of mitoNEET become oxidized, and the formed [2Fe-2S]-mitoNEET species reacts promptly to initiate Fe/S cluster transfer to IRP1, recycling the cytosolic apo-IRP1 into holo-aconitase. Until now, no clear data have been available on which is the system that reduces the mitoNEET clusters back once oxidative stress is not present anymore. In the present work, we used UV-vis and NMR spectroscopies to investigate the electron transfer process between mitoNEET and the cytosolic electron-donor Ndor1/anamorsin complex, a component of the cytosolic iron-sulfur protein assembly (CIA) machinery. The [2Fe-2S] clusters of mitoNEET are reduced via the formation of a transient complex that brings the [2Fe-2S] clusters of mitoNEET close to the redox-active [2Fe-2S] cluster of anamorsin. Our data provide in vitro evidence of a possible direct link between the CIA machinery and the mitoNEET cluster transfer repair pathway. This link might contribute to recovery of CIA machinery efficiency to mature cytosolic and nuclear Fe/S proteins.
人线粒体 NEET 是一种锚定在线粒体外部的同源二聚体蛋白，其 C 端位于细胞质中的 [2Fe-2S] 结合域。最近，人线粒体 NEET 被证明与细胞溶质铁调节蛋白 1（IRP1）的 Fe/S 簇修复有关，IRP1 是哺乳动物细胞中细胞内铁稳态的关键调节剂。线粒体 NEET 的 Fe/S 簇修复功能基于 Fe/S 氧化还原开关机制：在正常细胞条件下，存在还原的 [2Fe-2S]-线粒体 NEET，作为 Fe/S 簇转移蛋白是无活性的；在细胞氧化应激条件下，线粒体 NEET 的簇被氧化，形成的 [2Fe-2S]-线粒体 NEET 迅速反应，开始向 IRP1 转移 Fe/S 簇，将细胞溶质 apo-IRP1 再循环为 holo-aconitase。到目前为止，还没有明确的数据表明，一旦不存在氧化应激，哪种系统可以将线粒体 NEET 簇还原回原来的状态。在本工作中，我们使用 UV-vis 和 NMR 光谱学研究了线粒体 NEET 与细胞质电子供体 Ndor1/anamorsin 复合物之间的电子传递过程，Ndor1/anamorsin 复合物是细胞质铁硫蛋白组装（CIA）机制的一个组成部分。线粒体 NEET 的 [2Fe-2S] 簇通过形成瞬态复合物而被还原，该复合物使线粒体 NEET 的 [2Fe-2S] 簇靠近 anamorsin 的氧化还原活性 [2Fe-2S] 簇。我们的数据提供了 CIA 机制与线粒体 NEET 簇转移修复途径之间可能存在直接联系的体外证据。这种联系可能有助于恢复 CIA 机制对成熟细胞溶质和核 Fe/S 蛋白的效率。
