Involved in the control of epidermal-cell morphogenesis in roots and helical growth of roots by promoting microtubule depolymerization and limiting the accumulation of endoplasmic microtubules. Seems to be involved in the control of cell-file rotation (or twisting). Interacts (via C-terminus) with NEK5. A number of isoforms are produced. According to EST sequences. Expressed in the basal regions and petioles of immature leaves and in the root elongation zone. D-BOX motif functions as a recognition motif for the ubiquitination machinery. Belongs to the TRAFAC class myosin-kinesin ATPase superfamily. Kinesin family. Ungrouped subfamily.