Figure 4.

Rotation of an actin filament attached to the engineered F₁-ATPase with the γM23K mutation. (a) Rotation of the γM23K γ-subunit was recorded in the presence of 5 mM Mg-ATP (circles) or 0.5 mM Mg-ATP (triangles). Lines represent calculated rotational rates of the filaments with constant torque corrected for ATPase turnover: red dotted line, 30 pN⋅nm; blue dotted line, 80 pN⋅nm; solid green line, least square fitting of the experimental points gave an average torque of ≈50 pN⋅nm. Rotational rates were estimated as described in the legend to Fig. 2. (b) Rotational rates of γM23K subunit (red) are plotted together with those of the wild-type subunit (yellow) for direct comparison. (c) Calculated rotational rates of the filaments with constant torque not corrected for ATPase turnover are shown: red solid line, 10 pN⋅nm; red dotted line, 20 pN⋅nm; green solid line, 30 pN⋅nm; green dotted line, 40 pN⋅nm; blue solid line, 80 pN⋅nm. See legend to Fig. 2 for calculation.