Distinct roles of the FliI ATPase and proton motive force in bacterial flagellar protein export
Distinct roles of the FliI ATPase and proton motive force in bacterial flagellar protein export
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DOI：
10.1038/nature06449
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发表时间：
2008-01-24
期刊：
影响因子：
64.8
通讯作者：
Namba, Keiichi
中科院分区：
文献类型：
--
作者：
Minamino, Tohru;Namba, Keiichi
许多可溶性蛋白质以ATP酶驱动的方式跨细胞膜转运。为了构建负责运动性的细菌鞭毛，大多数组分通过鞭毛蛋白输出装置输出（1，2）。这种输出需要FliI ATP酶（3），其ATP酶活性受FliH调节（4）;然而，尚不清楚ATP水解产生的化学能如何用于输出过程。在这里，我们报告说，鞭毛蛋白的肠道沙门氏菌血清型鼠伤寒沙门氏菌的出口，即使在没有FliI。fliH fliI双无效突变体运动能力弱。形成输出门的核心的FlhA或FlhB中的某些突变实质上改善了双无效突变体的蛋白质输出和运动性。而且，质子动力对于输出过程至关重要。这些结果表明，FliH-FliI复合物仅促进输出底物最初进入门，ATP水解的能量用于从即将输出的蛋白质中分解和释放FliH-FliI复合物.底物的后续解折叠/易位过程的其余部分由质子动力驱动。
Translocation of many soluble proteins across cell membranes occurs in an ATPase- driven manner. For construction of the bacterial flagellum responsible for motility, most of the components are exported by the flagellar protein export apparatus(1,2). The FliI ATPase is required for this export(3), and its ATPase activity is regulated by FliH(4); however, it is unclear how the chemical energy derived from ATP hydrolysis is used for the export process. Here we report that flagellar proteins of Salmonella enterica serovar Typhimurium are exported even in the absence of FliI. A fliH fliI double null mutant was weakly motile. Certain mutations in FlhA or FlhB, which form the core of the export gate, substantially improved protein export and motility of the double null mutant. Furthermore, proton motive force was essential for the export process. These results suggest that the FliH - FliI complex facilitates only the initial entry of export substrates into the gate, with the energy of ATP hydrolysis being used to disassemble and release the FliH - FliI complex from the protein about to be exported. The rest of the successive unfolding/ translocation process of the substrates is driven by proton motive force.