Müller Judith M, Milenkovic Dusanka, Guiard Bernard, Pfanner Nikolaus, Chacinska Agnieszka
Institut für Biochemie und Molekularbiologie, Zentrum für Biochemie und Molekulare Zellforschung, Universität Freiburg, D-79104 Freiburg, Germany.
Mol Biol Cell. 2008 Jan;19(1):226-36. doi: 10.1091/mbc.e07-08-0814. Epub 2007 Oct 31.
The mitochondrial intermembrane space contains chaperone complexes that guide hydrophobic precursor proteins through this aqueous compartment. The chaperones consist of hetero-oligomeric complexes of small Tim proteins with conserved cysteine residues. The precursors of small Tim proteins are synthesized in the cytosol. Import of the precursors requires the essential intermembrane space proteins Mia40 and Erv1 that were proposed to form a relay for disulfide formation in the precursor proteins. However, experimental evidence for a role of Mia40 and Erv1 in the oxidation of intermembrane space precursors has been lacking. We have established a system to directly monitor the oxidation of precursors during import into mitochondria and dissected distinct steps of the import process. Reduced precursors bind to Mia40 during translocation into mitochondria. Both Mia40 and Erv1 are required for formation of oxidized monomers of the precursors that subsequently assemble into oligomeric complexes. Whereas the reduced precursors can diffuse back into the cytosol, the oxidized precursors are retained in the intermembrane space. Thus, oxidation driven by Mia40 and Erv1 determines vectorial transport of the precursors into the mitochondrial intermembrane space.
线粒体膜间隙含有伴侣蛋白复合物，可引导疏水性前体蛋白穿过这个水相区室。这些伴侣蛋白由具有保守半胱氨酸残基的小Tim蛋白的异源寡聚复合物组成。小Tim蛋白的前体在细胞质中合成。前体的导入需要膜间隙必需蛋白Mia40和Erv1，有人提出它们形成一个中继系统，用于前体蛋白中二硫键的形成。然而，一直缺乏Mia40和Erv1在膜间隙前体氧化中作用的实验证据。我们建立了一个系统，可直接监测前体导入线粒体过程中的氧化，并剖析导入过程的不同步骤。还原态的前体在转运到线粒体的过程中与Mia40结合。前体氧化单体的形成需要Mia40和Erv1，这些单体随后组装成寡聚复合物。还原态的前体可以扩散回细胞质，而氧化态的前体则保留在膜间隙中。因此，由Mia40和Erv1驱动的氧化决定了前体向线粒体膜间隙的向量运输。
