枯草芽孢杆菌(Bacillus subtilis)是生物安全的革兰氏阳性菌，可利用双精氨酸转运（Tat）系统分泌折叠成熟的蛋白质。Tat信号肽中典型的双精氨酸基序在识别膜转运组件中其重要的作用，但其与转运膜组件定向识别的分子机制及影响这一过程的机理目前尚不清楚。本研究拟以B.subtilis脂解酶LipA转运为模型，从体内和体外两个水平鉴定Tat系统引导LipA识别的转运途径，解析与LipA信号肽相互识别的膜转运组件，系统探讨LipA信号肽与膜转运组件之间互作的关键结构域及热点氨基酸对识别的影响和作用机制，阐明LipA信号肽与膜转运组件的识别以及LipA信号肽结构域的特性对Tat转运系统转运效率的影响作用及分子机制。此研究不仅为全面理解Tat转运早期影响底物转运的机理提供理论参考，也为阐明Tat底物校读/质量控制的分子机制奠定基础。

The twin-arginine translocation (Tat) is found in Bacillus subtilis that has a Generally Recognized As Safe (GRAS) status, in which the fully-folded cargo proteins are able to be secreted to the outer-space. The typical twin-arginine motiff within the Tat signal peptide is crutial for the recognition of membrane component in the translocation system. For clarifying the mechanism of Tat system in B.subtilis, the LipA is to be designated as the research model for this investigation. We firstly seek to identify the pathway in Tat system that mediating the LipA translocation in vitro and in vivo and unveil the membrane receptor interacting with signal-peptides within the translocation. On this basis, we will identify the essential domains and hot residues for the interaction between signal-peptide and key components in translocation. As well, the effect of those domains and key residues on signal-peptide-membrane receptor interaction will be elucidated respectively. Furthermore, we seek to explore the effect and mechanism of mutual recognition between signal-peptide and the corresponding membrane component. Specially, the contribution of features of Tat signal peptide to translocation functionality and efficiency will also be comprehensively explored and demonstrated. This project is critically important for mutually recognizing membrane receptor by signal-peptide in the course of Tat translocation. Furthermore, this investigation will provide comprehensive understand to that how those early occurrences effect on the substrate translocation. As well, it will guide to unveil the mechanism for substrate proofreading and quality control of Tat system.