Individual molecular motors use low forces to bypass roadblocks during collective cargo transport

A cargo encounters many obstacles during its transport by molecular motors
as it moves throughout the cell. Multiple motors on the cargo exert forces
to steer the cargo to its destination. Measuring these forces is essential
for understanding intracellular transport. Using kinesin as an example, we
measured the force exerted by multiple stationary kinesins in vitro,
driving a common microtubule. We find that individual kinesins generally
exert less than a piconewton (pN) of force, even while bypassing
obstacles, whether these are artificially placed 20-100 nm particles or
tau, a Microtubule Associated Protein. We demonstrate that when a kinesin
encounters an obstacle, the kinesin either becomes dislodged or switches
protofilaments while the other kinesins continue to apply their (sub-)pN
forces. By designing a high-throughput assay involving nanometer-resolved
multicolor-fluorescence and a force-sensor able to measure picoNewtons of
force, our technique is expected to be useful for many different types of
molecular motors.