Fig. 4

Tracking the myosin head with microsecond time resolution. a A trajectory of wild-type S1 in the direction of the major axis of the elliptically-shaped free diffusion (x-direction) in Fig. 3f. A histogram of the trajectory is shown side-by-side. The binding displacement was calculated by a hidden Markov model (Methods). b Two-step displacements by the transition from the detached state to the strong binding state. Cyan and magenta arrowheads indicate the end points of the two transitions. c A trajectory of lever-arm-less S1 in the direction of the major axis of the elliptically-shaped free diffusion. A histogram of the trajectory is shown side-by-side. d Step sizes of lever-arm-less S1 and wild-type, 33.3 ± 2.4 and 44.0 ± 2.4 nm, respectively. Error bars indicate SEM, n = 26 for each group, *p < 0.05 (p = 0.02, two-tailed unpaired t-test, Hedges’ g = 0.66). Center line, median; box limits, upper and lower quartiles; whiskers, 1.5x interquartile range; + , outliers. Experiments were performed at 2 μM ATP concentration. CI confidential interval. Data were obtained from at least 10 independent experiments. e Estimated geometry of the rigor complex. The geometry was estimated by the linker angle (Fig.1g, position 3) and the binding displacement (d).