A Critical Region in the FlaA Flagellin Facilitates Filament Formation of the Vibrio cholerae Flagellum
A Critical Region in the FlaA Flagellin Facilitates Filament Formation of the Vibrio cholerae Flagellum
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DOI：
10.1128/jb.00029-18
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发表时间：
2018-08-01
影响因子：
3.2
通讯作者：
Klose, Karl E.
中科院分区：
文献类型：
--
作者：
Echazarreta, Mylea A.;Kepple, Johnathan L.;Klose, Karl E.
霍乱弧菌是一种革兰氏阴性细菌，具有单毛鞭毛，可导致人类疾病霍乱。鞭毛介导的运动是宿主内和水环境中细菌生命周期的组成部分。霍乱弧菌鞭毛细丝由5个鞭毛蛋白亚基(FlaA、Flab、FLAC、Flad和FlaE)组成，但只有FlaA是合成鞭毛的必要条件和充分条件。FlaA是由III类鞭毛启动子转录而来，而其他四个鞭毛蛋白是由IV类启动子转录而来的。然而，表达来自IV类启动子的FlaA仍然促进了缺乏全部五种鞭毛蛋白(Delta Flaa-E)的菌株的运动。此外，来自副溶血性弧菌的FlaA(Vp)支持霍乱弧菌Delta Flaa-E株的运动，而来自创伤弧菌的FlaA(FlaA(Vv)；75%的同源性)不支持霍乱弧菌Delta Flaa-E株的运动，这表明FlaA的氨基酸序列在鞭毛合成中起关键作用。由FlaA(VC)和FLAD或FlaA(Vv)不同结构域组成的嵌合蛋白表明，N-末端D-1结构域(D-1N)包含FlaA功能所需的一个重要区域。对FlaA(VC)-Flad嵌合蛋白的进一步分析发现，在其他鞭毛的145位存在赖氨酸残基，但在FlaA(Vc)中没有赖氨酸残基，可以防止单丝形成。此外，插入到FlaA(Vv)中的FlaA(Vv)的氨基酸87到153的D-1N区域允许单丝形成，但不允许运动，显然是由于缺乏细丝曲率。这些结果确定了D-1N结构域中的残基，这些残基允许FlaA(Vc)折叠成功能细丝结构，并表明FlaA(Vc)帮助其他鞭毛的正确折叠。霍乱弧菌的感染导致了严重的腹泻疾病霍乱。它的游泳能力是通过极地鞭毛的旋转来调节的，这种运动性是它致病和在环境中生存的能力所不可或缺的。目前的研究阐明了多鞭毛蛋白结构中的一个特定鞭毛蛋白(FlaA)如何调节鞭毛细丝的形成，从而使霍乱弧菌得以游泳。这些知识可以导致更安全的疫苗和潜在的治疗方法来抑制霍乱。
Vibrio cholerae is a Gram-negative bacterium with a monotrichous flagellum that causes the human disease cholera. Flagellum-mediated motility is an integral part of the bacterial life cycle inside the host and in the aquatic environment. The V. cholerae flagellar filament is composed of five flagellin subunits (FlaA, FlaB, FlaC, FlaD, and FlaE); however, only FlaA is necessary and sufficient for filament synthesis. flaA is transcribed from a class III flagellar promoter, whereas the other four flagellins are transcribed from class IV promoters. However, expressing flaA from a class IV promoter still facilitated motility in a strain that was otherwise lacking all five flagellins (Delta flaA-E). Furthermore, FlaA from V. parahaemolyticus (FlaA(VP); 77% identity) supported motility of the V. cholerae Delta flaA-E strain, whereas FlaA from V. vulnificus (FlaA(VV); 75% identity) did not, indicating that FlaA amino acid sequence is responsible for its critical role in flagellar synthesis. Chimeric proteins composed of different domains of FlaA(VC) and FlaD or FlaA(VV) revealed that the N-terminal D-1 domain (D-1N) contains an important region required for FlaA function. Further analyses of chimeric FlaA(VC)-FlaD proteins identified a lysine residue present at position 145 of the other flagellins but absent from FlaA(VC) that can prevent monofilament formation. Moreover, the D-1N region of amino acids 87 to 153 of FlaA(VV) inserted into FlaA(VC) allows monofilament formation but not motility, apparently due to the lack of filament curvature. These results identify residues within the D-1N domain that allow FlaA(VC) to fold into a functional filament structure and suggest that FlaA(VC) assists correct folding of the other flagellins.IMPORTANCE V. cholerae causes the severe diarrheal disease cholera. Its ability to swim is mediated by rotation of a polar flagellum, and this motility is integral to its ability to cause disease and persist in the environment. The current studies illuminate how one specific flagellin (FlaA) within a multiflagellin structure mediates formation of the flagellar filament, thus allowing V. cholerae to swim. This knowledge can lead to safer vaccines and potential therapeutics to inhibit cholera.