Solution NMR Structure of the TatA Component of the Twin-Arginine Protein Transport System from Gram-Positive Bacterium Bacillus subtilis
Solution NMR Structure of the TatA Component of the Twin-Arginine Protein Transport System from Gram-Positive Bacterium Bacillus subtilis
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DOI：
10.1021/ja1053785
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发表时间：
2010-11-17
影响因子：
15
通讯作者：
Jin, Changwen
中科院分区：
文献类型：
--
作者：
Hu, Yunfei;Zhao, Enwei;Jin, Changwen
双精氨酸转运（达特）系统将折叠蛋白质转运穿过植物的细菌细胞质或叶绿体类囊体膜。大多数革兰氏阳性菌中的达特系统由两种基本组分组成，TatA和TatC蛋白。TatA被认为是一个双功能亚基，它可以通过自身寡聚化形成蛋白传导通道，也可以参与底物识别。然而，蛋白质转位的分子机制仍然是难以捉摸的。在这里，我们报告的溶液结构的TatA（d）蛋白质从枯草芽孢杆菌的NMR光谱，原子分辨率的达特系统的第一个结构。TatA（d）显示了由跨膜螺旋和两亲性螺旋形成的L形结构，而C-末端尾部大部分是非结构化的。我们的研究结果强烈支持TatA（d）的假设拓扑结构，其中跨膜螺旋插入到脂质双层中，而两亲性螺旋位于膜-水界面。此外，TatA（d）的结构揭示了铰链区几个保守残基的结构重要性，从而为进一步阐明达特系统的蛋白质转运机制提供了新的线索。
The twin-arginine transport (Tat) system translocates folded proteins across the bacterial cytoplasmic or chloroplast thylakoid membrane of plants. The Tat system in most Gram-positive bacteria consists of two essential components, the TatA and TatC proteins. TatA is considered to be a bifunctional subunit, which can form a protein-conducting channel by self-oligomerization and can also participate in substrate recognition. However, the molecular mechanism underlying protein translocation remains elusive. Herein, we report the solution structure of the TatA(d) protein from Bacillus subtilis by NMR spectroscopy, the first structure of the Tat system at atomic resolution. TatA(d) shows an L-shaped structure formed by a transmembrane helix and an amphipathic helix, while the C-terminal tail is largely unstructured. Our results strongly support the postulated topology of TatA(d) in which the transmembrane helix is inserted into the lipid bilayer while the amphipathic helix lies at the membrane-water interface. Moreover, the structure of TatA(d) revealed the structural importance of several conserved residues at the hinge region, thus shedding new light on further elucidation of the protein transport mechanism of the Tat system.