Role of the TOC complex in plastid protein import

TOC复合物在质体蛋白输入中的作用

• 批准号: 7077760
• 负责人: DANNY J. SCHNELL
• 金额: $ 26.48万
• 依托单位: UNIVERSITY OF MASSACHUSETTS AMHERST
• 依托单位国家: 美国
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-07-01 至 2009-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7077760
• 关键词: Arabidopsis; cell component structure /function; chloroplasts; guanine nucleotide binding protein; guanosinetriphosphatases; membrane transport proteins; nuclear membrane; photosynthetic reaction centers; plant genetics; plant proteins; protein binding; protein transport; yeast two hybrid system

DESCRIPTION (provided by applicant): Organelle identity and development rely on a complex set of intracellular protein trafficking systems that mediate the specific targeting of nuclear-encoded proteins to their proper subcellular compartment. Not only must these trafficking systems maintain a high degree of specificity, they must adapt to accommodate dramatic changes in the levels and composition of trafficking substrates imposed by developmental events. Defects in trafficking systems lead to numerous human disorders, including Zellweger syndrome (peroxisome biogenesis) and deafness/dystonia syndrome (mitochondrial protein import), or have lethal consequences that prevent cell growth and development. The study of protein import into plant chloroplasts is a powerful model for investigating protein trafficking and organelle biogenesis in eukaryotic cells because it allows combined biochemical and genetic analyses in a multicellular organism. The long-term goal of this research is to define the molecular mechanism of the import process and understand the role of import in plastid development. This proposal focuses on the role of two GTPases of the translocon at the outer envelope membrane of chloroplasts (Toc complex), Toc34 and Toc159, in preprotein recognition and the regulation of membrane translocation. We will test the hypothesis that Toc159 serves as the initial preprotein receptor and that GTP-regulated heterodimerization with Toc34 serves to regulate transfer of preproteins into the membrane translocation channel, thereby committing preproteins to the import pathway. To this end, we will take advantage of null mutants of Arabidopsis Toc159 (at Toc159) and Toc34 (atToc33) to establish the hierarchy of Toc GTPase function and examine the specific roles of each protein in the import reaction. In addition, combined biochemical and genetic approaches will be used to address the role of the GTPase activities of the Toc components in regulating preprotein recognition and access to the translocon channel. The final aim will test the hypothesis that the different members of the Toc159 and Toc34 families represent distinct pathways for protein targeting to plastids, and that separate pathways have evolved to ensure balanced import of essential proteins during plastid development. The structural basis for the formation and function of distinct translocons will be defined. This information, combined with information on the tissue-specific defects of mutants in each of the four at Toc159 genes, will provide insight into the roles of distinct protein import pathways during organelle and tissue development.

描述（由申请人提供）：细胞器的识别和发育依赖于一组复杂的细胞内蛋白运输系统，该系统介导核编码蛋白特异性靶向其适当的亚细胞区室。这些贩运系统不仅必须保持高度的特异性，而且必须适应发展事件造成的贩运基质的水平和构成的巨大变化。贩运系统的缺陷导致许多人类疾病，包括齐薇格综合征（过氧化物酶体生物发生）和耳聋/肌张力障碍综合征（线粒体蛋白输入），或具有阻止细胞生长和发育的致命后果。蛋白质导入植物叶绿体的研究是研究真核细胞中蛋白质运输和细胞器生物合成的有力模型，因为它允许在多细胞生物中进行生物化学和遗传分析。本研究的长期目标是确定导入过程的分子机制，并了解导入在质体发育中的作用。本文主要研究叶绿体外膜转位子的两个GTP酶Toc 34和Toc 159在前蛋白识别和膜转位调控中的作用。我们将测试的假设，Toc 159作为初始的前蛋白受体和GTP调节的异源二聚体与Toc 34用于调节前蛋白转移到膜转位通道，从而提交前蛋白的进口途径。为此，我们将利用拟南芥Toc 159（at Toc 159）和Toc 34（at Toc 33）的无效突变体来建立Toc GTdR功能的层次结构，并检查每个蛋白在输入反应中的特定作用。此外，生物化学和遗传学相结合的方法将被用来解决的TOC组件在调节前蛋白的识别和访问的translocon通道的GTdR活性的作用。最后的目标将测试的假设，Toc 159和Toc 34家族的不同成员代表不同的蛋白质靶向质体的途径，并单独的途径已经发展，以确保平衡进口的必需蛋白质在质体发育。不同的translocons的形成和功能的结构基础将被定义。这一信息，结合在Toc 159基因的四个突变体的组织特异性缺陷的信息，将提供洞察不同的蛋白质进口途径在细胞器和组织发育过程中的作用。