[EWS1-3] べん毛タンパク質輸送装置に装備された Na+駆動型輸送エンジンの活性化機構
The bacterial flagellum is a supramolecular motility machine responsible for rapid and efficient movement of bacterial cells towards more suitable environments. The flagellar type III protein export apparatus consists of a transmembrane export gate complex and a cytoplasmic ATPase complex and transports flagellar building blocks to the cell exterior to construct the bacterial flagella on the cell surface. The transmembrane export gate complex is equipped with two distinct H+- and Na+-driven export engines. Planktonic Salmonella wild-type cells predominantly use the H+-driven export engine under a variety of environmental conditions. However, when the flagellar ATPase complex does not function properly, the export engine opens its Na+ channel to continue the assembly of flagella on the cell surface. However, it remains unknown how the Na+-driven export engine is activated. In this symposium, I provide evidence that the FlgN chaperone acts as a switch to activate a backup export mechanism for the cytoplasmic ATPase complex by activating the Na+-driven engine and discuss why the Salmonella flagellar protein export apparatus maintains the Na+-driven export engine throughout the evolutionary process.