Fig. 5.

IFT velocities are recapitulated by simulations based on experimental parameters. (A) Dissociation rate measurements ($k_{\text{off}}$; solid circles; mean ± SE; $N=49–530$) for KIF17 (red) and KIF3AB (blue) as a function of load. Fits to dissociation rates (solid lines) were obtained by dividing fits to KIF17 and KIF3AB velocities (Fig. 2A) by the corresponding hindering- and assisting-load RL fits (Fig. 4B). Load-independent MT-binding rates ($k_{\text{on}}$; dashed lines) that generated IFT velocities that best agreed with in vivo findings (10) are shown (Fig. S4). (B) Simulated IFT velocities (circles; solid line) versus distance from the ciliary base compared with in vivo data (dashed line) from Prevo et al. (10). IFT velocities tend to be overestimated (empty circles) in the TZ (<1 µm from the base) and in the distal portions of the MS (beyond ∼2.8 µm; see text). (C) The total numbers of each type of motor on an IFT train as a function of distance from the base (dashed lines), measured by Prevo et al. (10) in vivo, graphed together with the numbers of MT-bound motors (circles; solid lines) based on the simulations (Materials and Methods). (Inset) The MT-bound motor data are rescaled to show greater detail. (D) Estimated percentage of total motors that are MT-bound as a function of distance, from the data in C. In C and D, solid circles are plotted in the region between 1.0 µm and 2.8 µm from the base; the TZ and distal MS are plotted using open circles. Velocities (B) and numbers of MT-bound motors (C and D) are mean values obtained from 40 Monte Carlo simulations (20,000 transitions each) sampled at 0.1-µm spacing (Materials and Methods) with $k_{17,\text{on}}=0.258\hspace{0.17em}{\mathrm{s}}^{-1}$ and $k_{3\text{AB},\text{on}}=0.244\hspace{0.17em}{\mathrm{s}}^{-1}$ (Fig. S4).