Molecular Mechanism of Mitochondrial Protein Import and Sorting

在线粒体蛋白质输入的过程中，各种胞浆因子起着重要的作用。我们在大鼠肝胞液中发现了一种新的胞液因子，该因子对N-乙基马来酰亚胺不敏感，这表明它与MSF并不完全不同。我们试图纯化该因子并对其进行部分表征。本实验还研究了粪卟啉原氧化酶（CPO，mitochondrial intermembrane space enzyme）的输入和缺失。CPO的前序列具有基质靶向和分选信号，并且前体在转化为成熟形式和定位于膜间隙之前被加工为中间形式。观察到两种类型的中间体。基质处理肽酶可能通过切割前体的两个识别位点形成两类中间体。此外，我们观察到氯化血红素抑制运输的前体进入大鼠线粒体，表明进口的前体血红素浓度调节。

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.