Synchronized Unidirectional-Rotation and Helical-Motion of Kinesin-Bound Gold Nanorods Indicates Coupling of Torque and Lateral-Force Generations of Kinesin Heads

Abstract

Kinesin has translational and rotational degrees of freedom and thus the kinesin motility is comprised of helical and rotational motions on a microtubule. However, the motility obtained by combination of helical and rotational motions remains elusive. Here we performed a comparative study of the multiple-motors motility of three plus-ended kinesins; processive single-headed KIF1A, weakly-processive double-headed ZEN-4 and non-processive single-headed kinesin-1 (sK1). Performing a gold-nanorod (GNR) motility assay, which enables us to measure the translational and rotational movements of kinesin-bound GNR around the suspended microtubule, we found that KIF1A-bound, ZEN-4-bound, and sK1-bound GNRs rotate 180° about the short axis of GNRs in one period of helical motion. The rotation-and-helix pitches were comparable between KIF1A-, ZEN-4- and sK1-GNRs (∼0.6 μm) while there were significant differences in their forward velocities. Theoretical analyses with the noise-driven 2D ratchet model indicates that the torque generation of kinesins is coupled to the force generation and that unidirectional rotation of the GNR driven by kinesins enhances biased sideward movement.