Tat转运系统的组装和信号肽识别的机制研究

Tat转运系统是细菌内膜上的折叠蛋白转运系统，负责将N端含有双精氨酸信号肽的胞质蛋白跨膜转运到周质空间。相比于Sec等非折叠蛋白转运系统，Tat转运系统转运折叠蛋白底物，这意味着其转运机理与众不同。Tat转运系统广泛存在于病原菌中，对其致病力具有重要作用。由于哺乳动物中缺少Tat转运系统，这使得抑制其正常工作的小分子药物具有低毒性的优点。然而，Tat转运系统的研究进展迟缓，尤其是Tat转运系统的整体组装机制和底物识别机制的缺乏，严重阻碍了我们对其工作机制的理解，从而限制了以Tat转运系统为靶标的药物开发。本项目旨在解析Tat转运系统整体复合物以及与双精氨酸信号肽的结构，结合基于结构的生化和功能实验，阐明Tat转运系统的整体组装机制以及对双精氨酸信号肽的识别机制，以期为探究Tat转运系统的工作机制提供重要基础，也为以Tat转运系统为靶标的药物研发提供线索。

The Tat transport system is a bacterial folded protein transport system in the inner membrane, which is responsible for transporting the cytoplasmic protein containing the amino-terminal twin-arginine signal peptide across the inner membrane to the periplasmic space. Compared with unfolded protein transport systems such as Sec, the Tat transport system transports folded proteins, which means that its transport mechanism is unique. The Tat transport system is widely distributed in pathogenic bacteria and plays an important role in its pathogenicity. Due to the lack of the Tat transport system in mammals, small molecule drugs that inhibit its working will have the advantage of low toxicity. However, the research progress of the Tat transport system has been slow, especially the lack of the overall assembly mechanism and substrate recognition mechanism, which has severely hindered our understanding of its working mechanism, thus limiting the development of drugs targeting the Tat transport system. In this project, we will determine the structures of the overall complex of the Tat transport system without and with the twin-arginine signal peptide, and perform structure-based biochemical and functional experiments, to clarify the overall assembly of the Tat transport system and the recognition mechanism of the twin-arginine signal peptide by Tat transport system. We hope this project will provide an important basis for the working mechanism of the Tat transport system, and also provides clues for development of drugs targeting the Tat transport system.