Abstract

Significance The kinesin-3 family is one of the largest among the kinesin superfamily and its members play important roles in a variety of cellular functions ranging from intracellular transport to mitosis. Defects in kinesin-3 transport have been implicated in a variety of neurodegenerative, developmental, and cancer diseases, yet the molecular mechanisms of kinesin-3 regulation and cargo transport are largely unknown. We show that kinesin-3 motors undergo cargo-mediated dimerization to transport cellular cargoes. We also show that dimerization results in kinesin-3 motors that are fast and superprocessive. Such high processivity has not been observed for any other motor protein and suggests that kinesin-3 motors are evolutionarily adapted to serve as the marathon runners of the cellular world.