Speed distribution of actin or actin-Tpm movement by ensembles of surface-immobilized motors. (A) Actin moved by Myo51 (n = 860), (B) actin-Tpm moved by Myo51 (n = 981), (C) actin moved by Myo51–Rng8/9 (n = 1,374), (D) actin-Tpm and Myo51–Rng8/9 (n = 1,515). The arrow indicates that ∼80% of all actin-Tpm filaments are nonmotile with Myo51–Rng8/9. The lines indicate the nonlinear fit of the data to the sum of an exponential decay and a Gaussian distribution (see supplemental Materials and methods). The mean ± SD of the Gaussian distribution is shown. Tpm slows motion powered by Myo51 (P < 0.05, t test comparing the Gaussian distributions). The presence of Rng8/9 on Myo51 increased the actin gliding speed of bare actin (P < 0.001, t test comparing Gaussian distributions).