Molecular Mechanism of Mitochondrial Protein Import and Sorting

在线粒体蛋白输入过程中，各种胞浆因子起着重要作用。我们在大鼠肝细胞浆中发现了新的胞浆因子，该因子对N-乙基马来酰亚胺不敏感，表明这与MSF并不完全不同。我们试图提纯这一因素，并对其进行了部分表征。根据我们的研究，这个因素很可能在线粒体蛋白前体和线粒体表面之间的识别过程中起作用。我们还检测了共比例卟啉原氧化酶(CPO，线粒体膜间间隙酶)的输入和缩短。CPO的前序列同时具有基质靶向和分选信号，前体被加工成中间形式，然后转化为成熟形式并定位到膜间隙。观察到两种中间体。基质加工肽酶可能通过切割前体的两个识别位点而形成两种中间体。此外，我们观察到氯化血红素抑制了前体向大鼠线粒体的运输，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.