Intracellular cargo transport by kinesin-3 motors

Intracellular transport along microtubules enables cellular cargoes to efficiently reach the extremities of large, eukaryotic cells. While it would take more than 200 years for a small vesicle to diffuse from the cell body to the growing tip of a one-meter long axon, transport by a kinesin allows delivery in one week. It is clear from this example that the evolution of intracellular transport was tightly linked to the development of complex and macroscopic life forms. The human genome encodes 45 kinesins, 8 of those belonging to the family of kinesin-3 organelle transporters that are known to transport a variety of cargoes towards the plus end of microtubules. However, their mode of action, their tertiary structure, and regulation are controversial. In this review, we summarize the latest developments in our understanding of these fascinating molecular motors.