Energy Transduction in Sodium Driven-flagagellar Motor

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Four motor proteins, MotX, MotY, PomA and PomB have been identified in the Na^+-type flagella of Vibrio spp. They are integral membrane proteins and essential components for the rotation of the Na^+-driven polar flagellar motor of Vibrio alginolyticus. To investigate PomA function, we carried out random mutagenesis of the pomA gene by using hydroxylamine. As the results, it is suggested that PomA and MotA of H^+ motor have very similar structure and roles. So the basic mechanism for torque generation will be similar in the proton and sodium motor. The complete motX gene was cloned from Vibrio alginolyticus and was shown to complement three mot mutations, motX94, motX115 and motX119, as well as a motX mutant of V.parahaemolyticus. The study of the flagellar motor has been intensively done in the H^+-motor and there are five core proteins (MotA, MotB, FliG, FliM and FliN) involved in the motor function. In the rotor part of the motor, three soluble proteins, FliG, FliM and FliN, are the components for force-generation, flagellar assembly and controlling the direction of motor rotation. Among them, FliG has a direct role in force generation with the cytoplaslmic region of MotA.We have clnoed the fliG gene of Na^+-driven polar flagellar motor and the product could be purified using the His tag. To verify whether the motor proteins form a complex, immunoprecipitation was carried out. PomB was coprecipitated with PomA by anti-PomA antibody, and anti-PomB antibody coprecipitated with PomA as well. Those directly demonstrated that PomA and PomB functionally interact with each other.