The role of mitochondria for molybdenum cofactor biosynthesis

本项目旨在研究线粒体在钼辅助因子（Moco）生物合成和钼酶活性中的作用。直到最近，人们普遍认为钼生物合成和钼酶形成只在细胞质中进行。然而，我们的初步工作表明，在Mocosynthesis和线粒体[Fe-S]簇的可用性之间存在串扰。已知线粒体内膜中的abc型转运体ATM3将[Fe-S]输出到细胞质中。然而，敲除ATM3不仅损害了[Fe-S]的输出，而且意外地导致前体z （moco生物合成的第一个中间体）的积累，而随后的moco生物合成的细胞质反应中间体的数量严重降低。这可能表明moco生物合成的第一步发生在线粒体中。在这个项目中，我们想要揭示前体z是否真的在线粒体内产生，如果是这样，催化前体z转化为钼酸蝶呤的酶复合物mpt合成酶是否与线粒体外膜有关。我们想要描述abc型转运体ATM3在moco生物合成中所起的作用。进一步，我们希望阐明线粒体对钼酶成熟的重要性，并提供Mocoand [Fe-S]-生物合成串扰的分子细节。不同方法的结合将使我们能够详细了解线粒体如何促进moco生物合成和细胞质中钼酶的形成。

It is the aim of this project to study the role of mitochondria for molybdenum cofactor (Moco) biosynthesis and molybdenum-enzyme activity. Until recently it was generally believed that Moco-biosynthesis and molybdenum-enzyme formation exclusively proceed in the cytoplasm. Our preliminary work, however, has shown that a crosstalk exists between Mocosynthesis and availability of [Fe-S]-clusters from mitochondria. The ABC-type transporter ATM3 in the inner membrane of mitochondria is known to export [Fe-S] into the cytoplasm. The knock-out of ATM3, however, impairs not only [Fe-S] export but unexpectedly leads to the accummulation of precursorZ (= first intermediate in Moco-biosynthesis) while the amounts of the subsequent cytoplasmic reaction intermediates of Moco-biosynthesis are severely lowered. This might indicate that the first step of Moco-biosynthesis takes place in mitochondria. - In this project we want to unveil whether precursorZ really is generated inside the mitochondria, and if so, whether the enzyme complex that catalyzes the conversion of precursorZ to molybdopterin, MPT-synthase, is associated with the outer membrane of mitochondria. We want to delineate the role played by the ABC-type transporter ATM3 for Moco-biosynthesis. Further we want to clarify the importance of mitochondria for the maturation of molybdenum-enzymes and provide molecular detail on the cross-talk of Mocoand [Fe-S]-biosynthesis. The combination of different approaches will allow us to get a detailed insight into how mitochondria contribute to Moco-biosynthesis and to the formation of molybdenum-enzymes in the cytoplasm.