Figure 2 : Torque-speed relationship of the Bacillus MotAB and MotPS motors.

From: Load- and polysaccharide-dependent activation of the Na+-type MotPS stator in the Bacillus subtilis flagellar motor

Figure 2

(a) Immunoblotting, using polyclonal anti-MotP (upper panel) and anti-MotS (lower panel) antibodies, of the membrane fractions prepared from ∆ABPS, BR151MA (wild type, indicated as WT), PAB-PS and Pgrac-PS strains. Each cropped blot was shown by a box. The positions of molecular mass markers were shown on the left. Relative MotP and MotS levels were normalized for wild-type level of each protein. These data were the average of at least three independent experiments. The experimental errors were within 10%. (b) Immunoblotting, using monoclonal anti-His-tag antibody, of membrane proteins extracted from the PAB-AB, PAB-PS, PAB-AB-His6 and PAB-PS-His6 strains. The relative level of MotP-His6 was normalized for the level of MotB-His6. At least three independent experiments were carried out. (c) Torque-speed relationship of the MotAB motor under 200 mM K+ (circle) or 200 mM Na+ (square) condition. Rotation measurements were carried out at 23 °C by tracking the position of 2.0-μm (yellow), 1.5-μm (orange), 1.0-μm (red), 0.8-μm (purple), 0.6-μm (cyan) and 0.5-μm (light green) beads attached to the partially sheared sticky filament. More than twenty individual beads of each size were measured. The curve was fitted by two straight lines with an intersection at the speed of 0.8-μm bead. (d) Torque-speed relationship of the MotPS motor. MotP and MotS were expressed from the PmotAB (square) or Pgrac promoter (triangle) in the presence of 200 mM NaCl. Rotation measurements were carried out at 23 °C by tracking the position of 1.5-μm, 1.0-μm, 0.8-μm, 0.6-μm and 0.5-μm beads attached to the sticky filament. The curve was fitted by two straight lines with an intersection at the speed of 0.6-μm (square) and 1.0-μm (triangle) bead. The expanded curve is shown in inset.