A Novel Signal Peptide-Based Protein Translocation System in the Thylakoids of Chloroplasts

叶绿体类囊体中基于信号肽的新型蛋白质易位系统

• 批准号: 9419287
• 负责人: Kenneth Cline
• 金额: --
• 依托单位: University of Florida
• 依托单位国家: 美国
• 项目类别: Continuing grant
• 财政年份: 1995
• 资助国家: 美国
• 起止时间: 1995-04-01 至 1999-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9419287&HistoricalAwards=false
• 关键词: Novel; Signal; Peptide; Based; Protein

9419287 Cline "Signal peptide" targeting sequences mediate protein translocation across several evolutionarily related membranes, ranging from the endoplasmic reticulum of eukaryotes to the cell membrane of bacteria. This proposal is concerned with the characterization of the novel protein transport machinery found in chloroplast thylakoids which is unique in that translocation is driven only by a pH gradient. Because proteins targeted to the thylakoid lumen are synthesized outside the chloroplast in the cytosol, there are two membrane systems which much be passed, the outer double membrane system and the the thylakoid membrane itself. The signal which targets the proteins past the outer double membrane system is cleaved from the protein, revealing the second part of the signal peptide which then interacts with the thylakoid protein transport machinery, or translocase. The objectives of the proposal are to purify the translocase, identify the pore complex associated with the translocase, assess the use of this pore by proteins which can use other translocases not driven solely by a pH gradient and vice versa, determine the location of the machinery on the thylakoid membrane system, and explore the possibility that such translocases might occur in E. coli. %%% Contemporary signal peptide-based transport systems have evolved from an archetypal mechanism. Yet each system has unique methods for targeting, initial insertion, and chain translocation, which are reflected by specific components and translocation requirements. In this context, it is expected that one thylakoid system, with its singular dependence on a pH gradient, has evolved a simpler, possibly more efficient mechanism for translocation. Results of this study should provide insight into the mechanism of pH gradient-driven translocation mechanisms. It will also provide tools to explore the relationship between envelope and thylakoids during the early developmental stages of thylakoid forma tion. The work proposed will have impact on our knowledge of the mechnanism and evolution of protein translocation across membranes in general. ***

9419287 Cline“信号肽”靶向序列介导蛋白质在几个进化相关的膜上的易位，从真核生物的内质网到细菌的细胞膜。这一建议是关于在叶绿体类囊体中发现的新型蛋白质运输机制的表征，其独特之处在于易位仅由pH梯度驱动。由于以类囊体管腔为靶点的蛋白质是在叶绿体外的细胞质中合成的，因此有两个膜系统可以通过，即外双膜系统和类囊体膜本身。通过外双膜系统靶向蛋白质的信号被从蛋白质上切割出来，显示出信号肽的第二部分，然后与类囊体蛋白质运输机制或转位酶相互作用。该提案的目标是纯化转位酶，鉴定与转位酶相关的孔复合物，评估蛋白质对该孔的使用，这些蛋白质可以利用不完全由pH梯度驱动的其他转位酶，反之亦然，确定该机制在类囊体膜系统上的位置，并探索这种转位酶可能发生在大肠杆菌中的可能性。当代基于信号肽的转运系统是从一种原型机制进化而来的。然而，每个系统都有独特的靶向、初始插入和链易位方法，这反映在特定的成分和易位要求上。在这种情况下，预计一个类囊体系统，其单一的依赖于pH梯度，已经进化出一个更简单，可能更有效的转运机制。本研究的结果将有助于深入了解pH梯度驱动的转运机制。它还将为探索类囊体形成早期发育阶段包膜和类囊体之间的关系提供工具。所提出的工作将对我们对蛋白质跨膜易位的机制和进化的认识产生影响。＊＊＊