ROLE OF THE FLIA-FLGM REGULATORY SYSTEM ON THE TRANSCRIPTIONAL CONTROL OF THE FLAGELLAR REGULON AND FLAGELLAR FORMATION IN SALMONELLA-TYPHIMURIUM
ROLE OF THE FLIA-FLGM REGULATORY SYSTEM ON THE TRANSCRIPTIONAL CONTROL OF THE FLAGELLAR REGULON AND FLAGELLAR FORMATION IN SALMONELLA-TYPHIMURIUM
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DOI：
10.1128/jb.176.12.3598-3605.1994
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发表时间：
1994-06-01
影响因子：
3.2
通讯作者：
IINO, T
中科院分区：
文献类型：
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作者：
KUTSUKAKE, K;IINO, T
在鼠伤寒沙门氏菌的鞭毛调节子中，鞭毛操纵子根据转录层次分为三类，1、2和3。2类操纵子受1类基因flhD和flhC正控制。第3类操纵子由fliA正向控制，由flgM负向控制。已经显示FliA是对3类特异性的σ因子，而FlgM是结合FliA以防止其与RNA聚合酶核心酶结合的抗σ因子。因此，FliA-FlgM调节系统被认为特异性控制3类操纵子。在本研究中，我们发现flgM突变增强了类2的表达超过五倍。当fliA突变同时存在时，没有观察到这种增强。这些结果表明，FliA-FlgM调节系统不仅参与3类的表达，而且参与2类的表达。然而，尽管flhD和flhC突变体都不能表达2类操纵子，但fliA突变体允许这些操纵子的基础水平表达。因此，FlhD和FlhC是必不可少的2类的表达，而FlgM耗竭条件下，其增强所需的，而FlhD和FlhC。此外，我们搁置了flgM突变导致鞭毛数量增加2至3倍。根据这些结果，我们提出，相对浓度的FliA和FlgM可能发挥重要作用，在确定鞭毛数量由一个单一的细胞。
In the flagellar regulon of Salmonella typhimurium, the flagellar operons are divided into three classes, 1, 2, and 3, with respect to transcriptional hierarchy. The class 2 operons are controlled positively by the class 1 genes, flhD and flhC. The class 3 operons are controlled positively by fliA and negatively by flgM. It has been shown that FliA is a sigma factor specific for class 3, whereas FlgM is an anti-sigma factor which binds FliA to prevent its association with RNA polymerase core enzyme. Therefore, the FliA-FlgM regulatory system has been believed to control specifically the class 3 operons. In the present study, we showed that the flgM mutation enhanced the expression of class 2 by more than fivefold. When a fliA mutation was present simultaneously, this enhancement was not observed. These results indicate that the FliA-FlgM regulatory system is involved not only in the expression of class 3 but also in that of class 2. However, though neither flhD nor flhC mutants could express the class 2 operons, the fliA mutants permitted the basal-level expression of those operons. Therefore, FlhD and FlhC are indispensable for the expression of class 2, whereas FIM is required only for its enhancement in the FlgM depletion condition. Furthermore, we shelved that the flgM mutation resulted in a two- to threefold increase in flagellar number. On the basis of these results, we propose that the relative concentration of FliA and FlgM may play an important role in the determination of flagellar numbers produced by a single cell.