The mechanism of molybdenum cofactor-insertion into apo-enzymes of the sulfite oxidase-class

在项目的前一部分中，我们专注于钼辅助因子(Moco)-一种介导Moco在其合成位点和最终用户酶之间转移的结合蛋白。现在，在第二个项目阶段，我们将详细研究Moco插入本身的机制。为了更好地理解Moco插入靶酶，有必要为Moco供体和无Moco受体提供良好的表征系统。我们希望实现一些广泛的目标：(1)揭示Moco在Moco供体蛋白Cnx1（拟南芥）和nit9（神经孢子虫）上形成的机制。(2)表征了神经孢子菌亚硫酸盐氧化酶受体蛋白的无moco形式。与植物相比，神经孢子虫具有类似动物的亚硫酸盐氧化酶的两结构域形式，由moco结构域和hemo结构域组成。(3)揭示Moco插入载亚硫酸盐氧化酶的机制。与人类和其他哺乳动物一样，成熟和功能性的神经孢子虫亚硫酸盐氧化酶位于线粒体的膜间空间。在什么阶段和什么地方（细胞质？）膜间隙?)Moco插入？哪些机器提供Moco？

In the previous part of the project we had focused on the molybdenum cofactor (Moco)- binding proteins mediating transfer of Moco between the site of its synthesis and the final user enzymes. Now in the second project phase, we will focus in detail on the mechanism of Moco insertion itself. For a better understanding of Moco insertion into target enzymes it is essential to have well characterized systems available both for the Moco donor and for the Moco-free acceptor. There are a number of broad objectives that we wish to achieve: (1) Unveil the mechanism by which Moco is formed on the Moco donor protein Cnx1 (Arabidopsis) and Nit-9 (Neurospora). (2) Characterize the Moco-free form of the acceptor protein sulfite oxidase from Neurospora. In contrast to plants, Neurospora possesses the animal-like two-domain form of sulfite oxidase consisting of a Moco-domain and a hemedomain. (3) Unveil the mechanism by which Moco is inserted into apo-sulfite oxidase. Like in humans and other mammals, mature and functional Neurospora sulfite oxidase is localized in the intermembrane space of mitochondria. At what stage and where (cytosol? intermembrane space?) Moco becomes inserted? Which machinery provides Moco?