In vivo experiments do not support the charge zipper model for Tat translocase assembly.
In vivo experiments do not support the charge zipper model for Tat translocase assembly.
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DOI：
10.7554/elife.30127
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发表时间：
2017-08-31
期刊：
影响因子：
7.7
通讯作者：
Berks BC
中科院分区：
文献类型：
--
作者：
Alcock F;Damen MP;Levring J;Berks BC
双精氨酸转位酶（Tat）在细菌细胞质膜和植物类囊体膜之间运输折叠蛋白。Tat易位位点是由底物触发的TatA蛋白寡聚化形成的。Walther及其同事提出了TatA低聚物的结构模型，其中TatA单体使用静电“电荷拉链”自组装（Cell(2013) 132: 15945）。该模型得到了含有电荷反转取代的TatA变体的低聚状态的体外分析的支持。在这里，我们使用了TatA在大肠杆菌中的组装和功能的活细胞分析来重新评估TatA的带电残基的作用。我们的结果不支持充电拉链模型。相反，我们观察到位于TatA两亲螺旋上的带电残基的取代将TatA锁定在组装状态，这表明这些带电残基在TatA组装后的蛋白质易位步骤中起着关键作用。
The twin-arginine translocase (Tat) transports folded proteins across the bacterial cytoplasmic membrane and the plant thylakoid membrane. The Tat translocation site is formed by substrate-triggered oligomerization of the protein TatA. Walther and co-workers have proposed a structural model for the TatA oligomer in which TatA monomers self-assemble using electrostatic ‘charge zippers’ (Cell (2013) 132: 15945). This model was supported by in vitro analysis of the oligomeric state of TatA variants containing charge-inverting substitutions. Here we have used live cell assays of TatA assembly and function in Escherichia coli to re-assess the roles of the charged residues of TatA. Our results do not support the charge zipper model. Instead, we observe that substitutions of charged residues located in the TatA amphipathic helix lock TatA in an assembled state, suggesting that these charged residues play a critical role in the protein translocation step that follows TatA assembly.