FIGURE 3:

The Kinesin-5 tail domain induces pauses, increases run lengths, and decreases motility velocities of the minitetramer kinesin-5. A) Pauses (red) and periods of processive motility for hMBX motor (blue) were identified in trajectories based on the slope of the mean-squared displacement (α) calculated within a sliding window along the trajectory. Alpha fluctuates between ∼2 and ∼0 indicating processive and stationary motility (bottom). B) The MSD for the entire trajectories of hMBX motors were fit to an expression that describes periods of stationary pauses and motile events consisting of processive and diffusive movements, MSD = (φvt)^2+φ2Dt+2ε^2 where φ is the fraction of time in a motile state. HMBX motors pause more frequently. C) Plotting all local α-values reveals primarily processive motility (green), while hMBXt exhibits a bimodal distribution with peaks consistent with static binding (μ1) and processive motility (μ2; purple). D) Histograms showing the frame-to-frame velocity of hMBXt motors (purple; solid line) and hMBX motors (green; dotted line). hMBX motors move faster than hMBXt motors during the processive sections of trajectories. Velocities are similar during paused sections. E) The total run length for hMBX motors was fit with a single exponential distribution with mean μ. All trajectories > 3 frames were included (n = 2056 trajectories). Unless otherwise specified, n = 111 trajectories from three independent experiments for hMBX constructs and n = 143 trajectories from nine independent experiments for hMBXt constructs.