The twin-arginine protein translocation (Tat) system has been characterized in bacteria, archaea and the chloroplast thylakoidal membrane. This system is distinct from other protein transport systems with respect to two key features. Firstly, it accepts cargo proteins with an N-terminal signal peptide that carries the canonical twin-arginine motif, which is essential for transport. Second, the Tat system only accepts and translocates fully folded cargo proteins across the respective membrane. Here, we review the core essential features of folded protein transport via the bacterial Tat system, using the three-component TatABC system of Escherichia coli and the two-component TatAC systems of Bacillus subtilis as the main examples. In particular, we address features of twin-arginine signal peptides, the essential Tat components and how they assemble into different complexes, mechanistic features and energetics of Tat-dependent protein translocation, cytoplasmic chaperoning of Tat cargo proteins, and the remarkable proofreading capabilities of the Tat system. In doing so, we present the current state of our understanding of Tat-dependent protein translocation across biological membranes, which may serve as a lead for future investigations.

中文翻译：

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Tat系统运输折叠蛋白。

双精氨酸蛋白易位（Tat）系统已在细菌，古细菌和叶绿体类囊体膜中表征。就两个关键特征而言，该系统不同于其他蛋白质转运系统。首先，它接受带有N端信号肽的货物蛋白，该蛋白带有典型的双精氨酸基序，这对运输至关重要。其次，Tat系统仅接受和折叠完全折叠的货物蛋白穿过各自的膜。在这里，我们使用大肠杆菌的三组分TatABC系统和枯草芽孢杆菌的两组分TatAC系统，回顾了通过细菌Tat系统转运折叠蛋白的核心基本特征。作为主要例子。特别是，我们探讨了双精氨酸信号肽的特征，必需的Tat组分及其如何组装成不同的复合物，Tat依赖性蛋白易位的机制特征和能量学，Tat货物蛋白的胞质伴侣以及它们的卓越的校对能力。达制。在此过程中，我们介绍了我们对Tat依赖性蛋白跨生物膜转运的了解的当前状态，这可能会成为未来研究的线索。