Molecular Studies of a Mitochondrial Ion Channel

跨膜屏障的蛋白质转运在许多细胞功能中是重要的，包括信号传导、分泌、细胞器的生物发生、区室化和程序性细胞死亡。 一个研究得很多但了解得很少的例子是前体蛋白被导入线粒体的过程。 在这个细胞器的内膜和外膜中的一组复杂的蛋白质识别，分类和选择性地将前体转运到它们的最终目的地。 一个充满水的蛋白质孔称为多导通道（MCC）的内膜被假定在这一过程中发挥关键作用。 该项目有三个目标，其主要目标是确定MCC在蛋白质输入中的生理作用及其作用的分子基础。 MCC是输入孔的假设预测，干扰输入装置的其他组件将改变MCC的性质。 因此，将使用抗体处理和内膜异源寡聚输入装置的蛋白水解来检测对MCC活性的影响，如通过电生理学技术监测的。 MCC可能与其外膜对应物，一种称为PSC（肽敏感通道）的通道串联起作用。 如果外通道和内通道在蛋白质易位过程中相互作用，那么外膜复合物的结构变化也可能影响MCC活性。 因此，将分析外膜复合物的类似抗体和蛋白水解处理对MCC活性的影响。 来自遗传操作的线粒体的MCC活性的生物化学重建将用于鉴定MCC的蛋白质组分。 然后将通过质谱法分析这些组分以确定其氨基酸序列。 这些研究将为蛋白质输入线粒体的机制提供基本的新信息。

Protein translocation across membrane barriers is important in many cellular functions including signaling, secretion, biogenesis of organelles, compartmentalization, and programmed cell death. A much studied yet poorly understood example is the process by which precursor proteins are imported into mitochondria. A complex set of proteins in both the inner and outer membranes of this organelle recognizes, sorts and selectively translocates precursors to their final destinations. A water-filled proteinaceous pore called the multiple conductance channel (MCC) of the inner membrane is postulated to play a key role in this process. This project has three objectives related to its main goal of determining the physiological role of the MCC in protein import and the molecular basis of its action. The hypothesis that the MCC is the import pore predicts that interfering with other components of the import apparatus will change the properties of the MCC. Therefore, treatment with antibodies and proteolysis of the hetero-oligomeric import apparatus of the inner membrane will be used to test for effects on MCC activity as monitored by electrophysiological techniques. MCC may function in tandem with its outer membrane counterpart, a channel called PSC (for peptide-sensitive channel). If the outer and inner channels interact during protein translocation, then structural changes made to the outer membrane complex may also affect MCC activity. Therefore, similar antibody and proteolysis treatments of the outer membrane complex will be analyzed for effects on MCC activity. Biochemical reconstitution of MCC activity from genetically manipulated mitochondria will be used to identify protein components of the MCC. These components will then be analyzed by mass spectrometry to determine their amino acid sequences. Together the studies will provide fundamental new information on the mechanisms of protein import into mitochondria.