Structural and Functional Comparison of Salmonella Flagellar Filaments Composed of FljB and FliC
Structural and Functional Comparison of Salmonella Flagellar Filaments Composed of FljB and FliC
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DOI：
10.3390/biom10020246
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发表时间：
2020-02-01
期刊：
影响因子：
5.5
通讯作者：
Kato, Takayuki
中科院分区：
文献类型：
--
作者：
Yamaguchi, Tomoko;Toma, Shoko;Kato, Takayuki
细菌鞭毛是一种运动细胞器，由一根长螺旋状的丝状体和一个旋转马达组成，丝状体作为推进器，旋转马达驱动丝状体快速旋转以产生推力。鼠伤寒沙门氏菌具有两个鞭毛蛋白基因fljB和fliC，用于鞭毛丝的形成，并且以每代每个细胞10（-3）-10（-4）的频率自主转换它们的表达。我们在这里报告的差异，在高粘度条件下的结构和运动功能。在高粘度下，表达FljB的沙门氏菌菌株显示出比表达FliC的沙门氏菌菌株更高的运动性。为了研究这种运动差异的原因，我们通过电子低温显微镜对FljB细丝进行了结构分析，发现除了鞭毛蛋白最外层结构域D3的位置和方向之外，该结构与FliC细丝几乎相同。结构域D3的密度在FljB中比FliC低得多，表明FljB的结构域D3比FliC的结构域D3更灵活和移动的。这些差异表明，结构域D3不仅在改变丝状体的抗原性方面，而且在优化丝状体在不同条件下作为推进器的运动功能方面起着重要作用。
The bacterial flagellum is a motility organelle consisting of a long helical filament as a propeller and a rotary motor that drives rapid filament rotation to produce thrust. Salmonella enterica serovar Typhimurium has two genes of flagellin, fljB and fliC, for flagellar filament formation and autonomously switches their expression at a frequency of 10(-3)-10(-4) per cell per generation. We report here differences in their structures and motility functions under high-viscosity conditions. A Salmonella strain expressing FljB showed a higher motility than one expressing FliC under high viscosity. To examine the reasons for this motility difference, we carried out structural analyses of the FljB filament by electron cryomicroscopy and found that the structure was nearly identical to that of the FliC filament except for the position and orientation of the outermost domain D3 of flagellin. The density of domain D3 was much lower in FljB than FliC, suggesting that domain D3 of FljB is more flexible and mobile than that of FliC. These differences suggest that domain D3 plays an important role not only in changing antigenicity of the filament but also in optimizing motility function of the filament as a propeller under different conditions.