Figure 2.

Processive movement of human myosin VIIa dimer on single actin filaments. A, a representative stepping trace of HM7AΔTail/LZ in the presence of 2 mm ATP. The fluorescence images were captured at 3.3 fps. The solid line represents the best fit to the trajectory. The numbers in the panel are displacement in nm of each step. B, step-size distribution of HM7AΔTail/LZ. The mean step-size of forward and backward steps are 37.5 ± 13.9 nm (mean ± S.D., n = 521) and −23.7 ± 13.4 nm (S.D., n = 21), respectively. The black solid line shows the best fit to the Gaussian equation with parameters of 34.7 ± 11.5 nm (mean ± S.D.) and −17.2 ± 16.5 nm (S.D.) for forward steps and backward steps, respectively. C, dwell-time distribution of HM7AΔTail/LZ. The solid line shows the best fit to a single exponential equation, ke^−kt, where t and k represent time and rate constant (the first bin was excluded from the fitting). The average waiting time (τ = 1/k) is 3.4 ± 0.2 s (S.E., n = 387).