Tuning cargo run length via fractional change in kinesin number

Cargos in biological cells are often carried along microtubules by small ensembles of molecular motors. Predictive understanding of motility in cells therefore requires quantitative insights into how molecular motors function in the small-ensemble limit. Toward this goal, here we employed Monte Carlo simulations to examine the run length of cargos carried by 1-2 motors. Focusing on the key microtubule-based motor kinesin-1, our simulations utilized experimentally determined single-kinesin characteristics, and included alterations in single-motor on- and off-rates caused by cellular factors and physical load. We found that, compared to the single-motor case, a fractional increase in kinesin number enhances cargo run length and amplifies sensitivity to changes in single-kinesin on-rate and off-rate. These tuning effects are largely independent of solution viscosity over the range reported for cells. Together, our data indicate that kinesin number in the small-ensemble limit is a sensitive tuning parameter for cargo run length. We anticipate