Traffic of single-headed motor proteins KIF1A: Effects of lane changing

KIF1A kinesins are single-headed motor proteins which move on cylindrical nanotubes called microtubules (MTs). A normal MT consists of 13 protofilaments on which the equispaced motor binding sites form a periodic array. The collective movement of the kinesins on a MT is, therefore, analogous to vehicular traffic on multilane highways where each protofilament is the analog of a single lane. Does lane changing increase or decrease the motor flux per lane? We address this fundamental question here by appropriately extending a recent model [P. Greulich et al., Phys. Rev. E 75, 041905 (2007)]. By carrying out analytical calculations and computer simulations of this extended model, we predict that the flux per lane can increase or decrease with the increasing rate of lane changing, depending on the concentrations of motors and the rate of hydrolysis of ATP, the “fuel” molecules. Our predictions can be tested, in principle, by carrying out in vitro experiments with fluorescently labeled KIF1A molecules.

Figure 1

(Color online) A schematic representation of our model, together with the allowed transitions and the corresponding rate constants.

Figure 2

(Color online) Flux per lane (and, in the inset, average density of the motors on each lane) are plotted against ${\omega }_{fl}∕{\omega }_f$ for a few values of ${\omega }_s∕{\omega }_f$. Our mean-field predictions (labeled MF) are plotted by lines while the discrete data points (labeled Sim) have been obtained from our computer simulations of the model.

Figure 3

(Color online) Same as in Fig. 2, except that the data are plotted against $K$ for a few values of ${\omega }_{fl}∕{\omega }_f$.

Figure 4

(Color online) Same as in Fig. 2, except that the data are plotted against ${\omega }_h∕{\omega }_f$ for a few values of $K$.