Molecular Mechanism of Mitochondrial Protein Import and Sorting

在线粒体蛋白输入过程中，各种细胞质因子起着重要作用。我们在大鼠肝细胞质中发现了新的胞质因子，该因子对n -乙基马来酰亚胺不敏感，这表明这与MSF并没有完全不同。我们试图提纯这一因子，并对其进行了特殊表征。从我们的研究来看，这个因子可能在线粒体蛋白前体与线粒体表面的识别过程中起作用。我们还检测了线粒体膜间隙酶（coproporphyrinogen oxidase， CPO）的输入和缺失。CPO的前体具有基质靶向和分选信号，前体在转化为成熟形态并定位到膜间空间之前被加工成中间形态。观察到两种类型的中间体。基质加工肽酶可能通过切割前体的两个识别位点形成两种中间体。此外，我们观察到血红素抑制前体转运到大鼠线粒体，这表明前体的进口受到血红素浓度的调节。

In the process of mitochondrial protein import, various cytosolic factors play an important role. We found new cytosolic factor in rat liver cytosol and this factor was insensitive to N-ethylmaleimide, suggesting that this was not completely different from MSF. We tried to purify this factor and partiually characterized. From our research, it is likely that this factor works in the process of recognition between mitochondorial protein precursor and mitochondirial surface.We also examined import and shorting of coproporphyrinogen oxidase (CPO, mitochondrial intermembrane space enzyme). The presequence of CPO had both matrix targeting and sorting signal and the precursor was processed to the intermediate form before converting to mature form and localization to the intermembrane space. Two types of intermediates were observed. Matrix processing peptidase might form the two types of intermediates by cutting the two recognition site of the precursor. Moreover, we observed hemin inhibition of transport of the precursor into rat mitochondria, suggesting that import of the precursor was regulated by heme concentration.