Accurate measurements of motor rotation and proton current
     Bacterial flagellar motors are embedded in the cytoplasmic membrane and powered by the influx of ions according to the electrochemical potential gradient. Namely, the flagellar motors convert the electrochemical potential energy into mechanical work of rotation. To clarify the mechanism of energy conversion, it is important to measure the current of ions (input) and the rotation (output) of the motor. However, the ion current has not been measured accurately enough, and the rotation of the motor has not been directly measured at sufficiently high temporal resolution.
     To set up the system measuring both the ion current and the motor rotation, We mainly study the H+-driven flagellar motor of Salmonella. We develop methods to embed individual motor in a black membrane to measure proton currents through the motor that are expected to be at sub-picoampere level. For comparison of the effect of ion specificity, we also plan to study Na+-driven flagellar motor of alkalophilic Bacillus. Upon completion of the experimental system, we will investigate effects of mutations in vaious motor proteins on the relationship between the current and the rotation, which is expected to clarify the torque generation mechanism of the flagellar motors.