Clegg D O, Koshland D E
J Bacteriol. 1985 Apr;162(1):398-405. doi: 10.1128/jb.162.1.398-405.1985.
The Escherichia coli flaA gene product (also called cheC) plays a crucial role in switching flagellar rotational direction during chemotactic responses. Wild-type and mutant alleles have been cloned onto plasmid vectors, and the gene product has been identified as a 37,000-dalton protein. The flaA product appeared as a soluble protein in the cytoplasm when overproduced in minicells and maxicells. The protein could not be detected in flagellar basal structures purified from a wild-type strain. To assess the effects of altered flaA expression, the gene was fused to a synthetic tac promoter that could be regulated by the addition of an inducer. Overproduction resulted in strong counterclockwise flagellar rotational bias and partial paralysis of flagellar motors. These results suggest that the flaA protein provides the interface between the flagellar machinery and the chemotaxis signaling system in a motor structure external to the basal body.
大肠杆菌flaA基因产物（也称为cheC）在趋化反应过程中切换鞭毛旋转方向时起着关键作用。野生型和突变等位基因已被克隆到质粒载体上，并且该基因产物已被鉴定为一种37000道尔顿的蛋白质。当在小细胞和大细胞中过量表达时，flaA产物在细胞质中表现为可溶性蛋白质。在从野生型菌株纯化的鞭毛基部结构中检测不到该蛋白质。为了评估flaA表达改变的影响，该基因与一个可通过添加诱导剂进行调控的合成tac启动子融合。过量表达导致强烈的逆时针鞭毛旋转偏向和鞭毛马达部分麻痹。这些结果表明，flaA蛋白在基体外部的马达结构中提供了鞭毛机制与趋化信号系统之间的界面。
