Graduate School of Natural Science and Technology, Department of Biology, Faculty of Science, Okayama University, Tsushima-Naka 3-1-1, Kita-ku, Okayama 700-8530, Japan.
J Bacteriol. 2011 Oct;193(19):5191-8. doi: 10.1128/JB.05441-11. Epub 2011 Jul 29.
YdiV acts as an anti-FlhD4C2 factor, which negatively regulates the class 2 flagellar operons in poor medium in Salmonella enterica serovar Typhimurium. On the other hand, one of the class 2 flagellar genes, fliZ, encodes a positive regulator of the class 2 operons. In this study, we found that the FliZ-dependent activation of class 2 operon expression was more profound in poor medium than in rich medium and not observed in the ydiV mutant background. Transcription of the ydiV gene was shown to increase in the fliZ mutant. Purified FliZ protein was shown in vitro to bind to the promoter region of the nlpC gene, which is located just upstream of the ydiV gene, and to repress its transcription. These results indicate that FliZ is a repressor of the nlpC-ydiV operon and activates the class 2 operons by repressing ydiV expression. Therefore, the fliZ and ydiV genes form a regulatory loop.
YdiV 作为一种抗 FlhD4C2 因子，在沙门氏菌鼠伤寒血清型中负调控贫营养培养基中的 2 类鞭毛操纵子。另一方面，2 类鞭毛基因之一 fliZ 编码 2 类操纵子的正调控因子。在本研究中，我们发现 FliZ 对 2 类操纵子表达的激活在贫营养培养基中比在富营养培养基中更为明显，而在 ydiV 突变体背景中则观察不到。ydiV 基因的转录显示在 fliZ 突变体中增加。体外纯化的 FliZ 蛋白被证明能结合位于 ydiV 基因上游的 nlpC 基因启动子区域，并抑制其转录。这些结果表明 FliZ 是 nlpC-ydiV 操纵子的阻遏物，并通过抑制 ydiV 的表达来激活 2 类操纵子。因此，fliZ 和 ydiV 基因形成一个调控环。
