Indiana University, Department of Biology, Bloomington, Indiana, USA.
J Bacteriol. 2012 Sep;194(17):4619-29. doi: 10.1128/JB.00444-12. Epub 2012 Jun 22.
The structure of the Gram-positive flagellum is poorly understood, and Bacillus subtilis encodes three proteins homologous to the flagellar hook protein from Salmonella enterica. Here we generated a modified B. subtilis hook protein that could be fluorescently stained using a cysteine-reactive dye. We used the fluorescently labeled hook to demonstrate that FlgE is the hook structural protein and that FliK regulated hook length. We further demonstrate that two proteins of unknown function, FlhO and FlhP, and the putative hook cap, FlgD, were required for hook assembly, such that when flhO, flhP, or flgD was mutated, hook protein was secreted into the supernatant. All mutants defective in hook completion resulted in homogeneously reduced σ(D)-dependent gene expression due to the action of the anti-sigma factor FlgM.
革兰氏阳性菌鞭毛的结构尚未完全阐明，枯草芽孢杆菌编码了三种与沙门氏菌鞭毛钩蛋白同源的蛋白。在这里，我们生成了一种经过改良的枯草芽孢杆菌钩蛋白，它可以使用半胱氨酸反应性染料进行荧光染色。我们使用荧光标记的钩蛋白来证明 FlgE 是钩状结构蛋白，并且 FliK 调节钩的长度。我们进一步证明，两个功能未知的蛋白 FlhO 和 FlhP，以及假定的钩帽蛋白 FlgD，是钩组装所必需的，因此当 flhO、flhP 或 flgD 突变时，钩蛋白会被分泌到上清液中。由于抗σ因子 FlgM 的作用，所有完成钩状结构缺陷的突变体导致 σ(D)-依赖性基因表达均匀减少。
