Fig. 3.

Dependence of motor speed on motor density. (A) Kymograph (inverted contrast) showing the movement of individual Kip3-EGFP molecules in the presence of Kip3-mCherry (3.2 nM, not shown). Tracked data points (green) were used to calculate the indicated velocities. Red dashed lines represent the traffic jam boundary (Left) and the end of the microtubule (Right). (B) Simulated trajectories from Fig. 1C. (C) Experimental relationship between motor speed and motor density in the presence of 30 mM KCl (blue points, 0 and 3.2 nM Kip3-mCherry) and 110 mM KCl (orange points, 0 to 6.4 nM Kip3-mCherry). (Inset) Lattice-dissociation rate (s^-1) vs. motor density at 110 mM salt. (D) Simulated relationship between the normalized motor speed and density using the parameters: with N = 1,250, , and (equivalent to 2 nM Kip3) (blue points); with N = 1,250, , and (equivalent to 8 nM Kip3) (orange points).