FIGURE 7.

The impact of multistate detachment when applied loads vary spatially. When multiple motors experience spatially dependent applied loads, the partial detachment of a complex leads to rearward cargo displacements that can reduce the load on the bead. Because these displacements are accompanied by changes in the number of bound motors, this process affects the force-dependent probability that a complex will be bound via a single or both motor molecules of a complex. Measurements of reward displacement sizes in a static optical trap (κ_trap = 0.072 pN/nm) indicate that the applied load changes by 4–5 pN on average upon partial bead detachment if it exceeds kinesin's 7 pN stalling force. Such large changes in load can result in a significant reduction in the probability that a two-kinesin complex will be bound via a single motor within this force regime, and therefore result in higher cargo velocities, on average, relative to cases where the applied load remains constant or varies weakly as a function of cargo position. The lines in the plot depict exponential fits to the static trapping data.