Molecular Mechanism of Protein Transport into Chloroplasts

植物细胞中的许多重要代谢途径都发生在叶绿体中。尽管这些过程所需的一些蛋白质和酶是在叶绿体自身内合成的，但这些蛋白质中的绝大多数是作为前体在植物细胞的细胞质中合成的，随后被运输到叶绿体中。这些蛋白质进入叶绿体是通过位于叶绿体表面的一个输入装置来调节的。该项目的长期目标是确定构成模式植物Arabadasis的输入装置的蛋白质，并阐明输入装置的单个蛋白质对前体蛋白向叶绿体运输的生化机制。这个项目使用遗传方法来研究选定的蛋白质的功能，这些蛋白质作为进口机械的分子马达，通过提供运输过程的驱动力。将构建转基因植物，在其中正常的阿拉伯领养蛋白要么被灭活，要么被改变形式的蛋白质取代。然后将使用细胞生物学和生化实验来评估基因改变对运输过程的影响。将在表达一种改变的蛋白质或多种改变的蛋白质的植物中研究这种运输过程。这一策略将阐明单个蛋白质的功能，并提供关于不同蛋白质之间相互作用的信息。从这个项目中得出的对蛋白质输入的新理解将有助于工程各种叶绿体特定代谢途径的努力。例如，合成独特脂肪酸的新型酶可以针对叶绿体，创造具有改善营养或工业价值的修饰脂肪酸的植物。因此，这项研究不仅将增进我们对以叶绿体为靶标的蛋白质的基本理解，还将通过提高我们为各种用途设计和修饰植物的能力而产生实际影响。

Many essential metabolic pathways in plant cells occur within the chloroplast. Although some of the proteins and enzymes required for these processes are synthesized within the chloroplast itself, the vast majority of these proteins are synthesized as precursors in the cytoplasm of plant cells and are subsequently transported into chloroplasts. Import of these proteins into chloroplasts is mediated by an import apparatus located on the chloroplast surface. The long-term goal of this project is to identify the proteins that constitute the import apparatus of the model plant Arabadopsis and to clarify the biochemical mechanisms by which individual proteins of the import apparatus contribute to the transport of precursor proteins into chloroplasts. This project uses a genetic approach to investigate the function of selected proteins that operate as the molecular motor of the import machinery, by providing the driving force for the transport process. Transgenic plants will be constructed in which the normal Arabadopsis protein has been either inactivated or replaced with an altered form of the protein. Cell biological and biochemical experiments will then be used to evaluate the effect of the gene alterations on the transport process. The transport process will be studied in plants expressing either one altered protein or multiple altered proteins. This strategy will elucidate the functions of individual proteins and also provide information about interactions between the various proteins. The new understanding of protein import derived from this project will be useful for efforts that involve the engineering of various chloroplast-specific metabolic pathways. For instance, novel enzymes that synthesize unique fatty acids could be targeted to chloroplasts to create plants with modified fatty acids that have improved nutritional or industrial value. Hence, this research will both advance our basic understanding of protein targeting to chloroplasts and have the practical impact by improving our ability to engineer and modify plants for a variety of uses.