Fig. 4.

Dual-colored Qdot-labeled FLB- and HMM-myoV stepping dynamics. Representative displacement vs. time traces for dual-labeled HMM-myoV (A) and FLB-myoV (B) at 100 mM KCl and 10 μM ATP, captured at 15 fps. (A) HMM-myoV exhibits almost exclusively (94%) hand-over-hand stepping. The bar chart shows the percentage of motor steps for which it took one (1) or two or more (≥2) steps before the heads switch roles between leading and trailing, and the occurrence of backward (BK) steps. (B) FLB-myoV has a mixture of hand-over-hand (60%) and altered gating (33%) steps where the motor took ≥2 steps before the heads switched roles (highlighted by dashed box). FLB-myoV also took occasional (7%) backward (BK) steps, identified by an arrow in the trace. (C) Interhead distances for the HMM-myoV (red bars) fit to a Gaussian (34 ± 2 nm) and the FLB-myoV (gray bars).