Subunit organization in the TatA complex of the twin arginine protein translocase: a site-directed EPR spin labeling study.
Subunit organization in the TatA complex of the twin arginine protein translocase: a site-directed EPR spin labeling study.
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DOI：
10.1074/jbc.m109.065458
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发表时间：
2010-01-22
期刊：
影响因子：
--
通讯作者：
Thomson AJ
中科院分区：
文献类型：
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作者：
White GF;Schermann SM;Bradley J;Roberts A;Greene NP;Berks BC;Thomson AJ
达特系统用于运输折叠蛋白质穿过细菌和古细菌的细胞质膜以及植物叶绿体的类囊体膜。完整膜TatA蛋白的多聚体被认为形成达特途径的蛋白传导元件。氮氧自由基在选定的位置内的跨膜螺旋的大肠杆菌TatA和用于探测洗涤剂溶解的TatA复合物的结构，通过EPR光谱。自旋标记迁移率的比较允许个别残基的分类内的TatA复合物或暴露在表面，并建议残基Ile12和Val14参与螺旋之间的相互作用。自旋间距离的分析表明，TatA亚基的跨膜螺旋排列为一个单壁环，包含一个亚基上的Ile12和相邻亚基上的Val14之间的接触界面。将标记的和未标记的TatA样品混合的实验证明TatA亚基在TatA复合物之间交换。这一观察结果与达特转运机制的TatA动态聚合模型一致。
The Tat system is used to transport folded proteins across the cytoplasmic membrane in bacteria and archaea and across the thylakoid membrane of plant chloroplasts. Multimers of the integral membrane TatA protein are thought to form the protein-conducting element of the Tat pathway. Nitroxide radicals were introduced at selected positions within the transmembrane helix of Escherichia coli TatA and used to probe the structure of detergent-solubilized TatA complexes by EPR spectroscopy. A comparison of spin label mobilities allowed classification of individual residues as buried within the TatA complex or exposed at the surface and suggested that residues Ile12 and Val14 are involved in interactions between helices. Analysis of inter-spin distances suggested that the transmembrane helices of TatA subunits are arranged as a single-walled ring containing a contact interface between Ile12 on one subunit and Val14 on an adjacent subunit. Experiments in which labeled and unlabeled TatA samples were mixed demonstrate that TatA subunits are exchanged between TatA complexes. This observation is consistent with the TatA dynamic polymerization model for the mechanism of Tat transport.