Figure 3. Estimation of the number of active stators in the MotAB and MotPS motors.
The (a) MotAB or (b) MotPS stator was expressed from an IPTG-inducible Pgrac promoter by addition of 0.1 mM IPTG. After incubation for 30 min, rotation measurements were carried out at 23 °C by tracking the position of 1.0-μm beads attached to the partially sheared sticky filament in motility buffer containing 1.0 mM IPTG and 200 mM NaCl. The traces and speed histograms are shown on the left and middle. The relationship of the stator number and speed obtained from multiple Gaussian function of speed histograms is shown on the right. A set of data was fitted by second-order polynomial function. The horizontal solid or dash line shows the average speed of each motor when expressed from the PmotAB or Pgrac promoter, respectively.