Molecular mechanism and structure of the cytosolic iron-sulfur protein assembly (CIA) machinery

铁硫（Fe/S）簇是必需的蛋白质辅助因子，参与许多关键的生物过程，如代谢、能量转换、DNA合成和修复以及蛋白质翻译。铁/硫簇的合成及其插入活细胞中的靶蛋白是由复杂的机械催化的。在（非绿色）真核生物中，线粒体和细胞质中已经鉴定出三种生物发生系统，已知成分超过30种。线粒体Fe/S蛋白需要铁硫簇（ISC）组装机制，该机制在进化过程中遗传自细菌。胞质和细胞核铁硫蛋白的生物发生也依赖于该机制的功能，但还需要线粒体ISC输出装置和胞质铁硫蛋白组装（CIA）机制。迄今为止，已经鉴定了11种CIA蛋白，并确定了它们的作用序列，但对它们的生化功能知之甚少。因此，本研究旨在阐明三种CIA蛋白复合物的分子机制。细胞生物学和生化重建方法将与超微结构和突变技术相结合，以确定[4Fe-4S]簇如何最初在CIA支架复合物上合成，然后通过CIA靶向和适配器复合物特异性插入靶载脂蛋白的分子事件。我们的研究将有助于解决复杂的分子机制的中心和保守的生命过程。

Iron-sulfur (Fe/S) clusters are essential protein cofactors involved in numerous key biological processes such as metabolism, energy conversion, DNA synthesis and repair, and protein translation. The synthesis of Fe/S clusters and their insertion into target proteins in a living cell is catalyzed by complex machinery. In (non-green) eukaryotes three biogenesis systems have been identified in mitochondria and cytosol with more than 30 known components. Mitochondrial Fe/S proteins require the iron-sulfur cluster (ISC) assembly machinery which was inherited from bacteria during evolution. Biogenesis of cytosolic and nuclear Fe/S proteins also depends on the function of this machinery, yet additionally requires the mitochondrial ISC export apparatus and the cytosolic iron-sulfur protein assembly (CIA) machinery. Hitherto, eleven CIA proteins have been identified and their sequence of action been defined, yet little is known about their biochemical function. This proposal therefore aims to elucidate the molecular mechanisms of three CIA protein complexes. Cell biological and biochemical reconstitution approaches will be combined with ultrastructural und mutational techniques to define the molecular events of how a [4Fe-4S] cluster is initially synthesized on the CIA scaffold complex and then specifically inserted into target apoproteins via the CIA targeting and adapter complexes. Our studies will help resolving the sophisticated molecular mechanisms of a central and conserved process of life.