FlhF and Its GTPase Activity Are Required for Distinct Processes in Flagellar Gene Regulation and Biosynthesis in Campylobacter jejuni
FlhF and Its GTPase Activity Are Required for Distinct Processes in Flagellar Gene Regulation and Biosynthesis in Campylobacter jejuni
复制标题
DOI：
10.1128/jb.00884-09
复制
发表时间：
2009-11-01
影响因子：
3.2
通讯作者：
Hendrixson, David R.
中科院分区：
文献类型：
--
作者：
Balaban, Murat;Joslin, Stephanie N.;Hendrixson, David R.
FlhF蛋白是推定的GTP酶，其通常是极鞭毛细菌中鞭毛细胞器发育中的一个或多个步骤所必需的。在空肠弯曲菌中，FlhF是sigma（54）依赖性鞭毛基因表达和鞭毛生物合成所必需的，但FlhF如何影响这些过程尚不清楚。此外，任何FlhF蛋白的GT酶活性和鞭毛生物合成步骤中这种推测活性的要求仍然没有表征。我们在这里表明，C。空肠FlhF水解GTP，表明这些蛋白是GTP酶。C.与缺乏FlhF的突变体不同，产生具有降低的GTT酶活性的FlhF蛋白的空肠突变体对于σ（54）依赖性鞭毛基因表达没有严重缺陷。相反，这些突变体有一种倾向，缺乏鞭毛或产生鞭毛在不适当的数量或在非极性的位置，表明GTP水解FlhF是必要的适当的鞭毛生物合成。进行了集中于阐明FlhF在σ（54）依赖性鞭毛基因表达中的可能作用的另外的研究。这些研究表明，FlhF不影响鞭毛输出装置和FlgSR双组分调节系统之间的信号传导或产生信号以激活sigma（54）。相反，我们的数据表明，FlhF的功能在一个独立的途径，收敛或下游的鞭毛输出装置-FlgSR途径影响西格玛（54）依赖的基因表达。这项研究提供了确凿的生化和遗传分析表明，不同的活动，C。空肠FlhF GT3是鞭毛基因表达和生物合成中不同步骤所必需的。我们的研究结果可能适用于许多极性鞭毛细菌，利用FlhF鞭毛生物合成过程。
FlhF proteins are putative GTPases that are often necessary for one or more steps in flagellar organelle development in polarly flagellated bacteria. In Campylobacter jejuni, FlhF is required for sigma(54)-dependent flagellar gene expression and flagellar biosynthesis, but how FlhF influences these processes is unknown. Furthermore, the GTPase activity of any FlhF protein and the requirement of this speculated activity for steps in flagellar biosynthesis remain uncharacterized. We show here that C. jejuni FlhF hydrolyzes GTP, indicating that these proteins are GTPases. C. jejuni mutants producing FlhF proteins with reduced GTPase activity were not severely defective for sigma(54)-dependent flagellar gene expression, unlike a mutant lacking FlhF. Instead, these mutants had a propensity to lack flagella or produce flagella in improper numbers or at nonpolar locations, indicating that GTP hydrolysis by FlhF is required for proper flagellar biosynthesis. Additional studies focused on elucidating a possible role for FlhF in sigma(54)-dependent flagellar gene expression were conducted. These studies revealed that FlhF does not influence production of or signaling between the flagellar export apparatus and the FlgSR two-component regulatory system to activate sigma(54). Instead, our data suggest that FlhF functions in an independent pathway that converges with or works downstream of the flagellar export apparatus-FlgSR pathway to influence sigma(54)-dependent gene expression. This study provides corroborative biochemical and genetic analyses suggesting that different activities of the C. jejuni FlhF GTPase are required for distinct steps in flagellar gene expression and biosynthesis. Our findings are likely applicable to many polarly flagellated bacteria that utilize FlhF in flagellar biosynthesis processes.