Enhanced processivity and collective force production of kinesin-1 at low radial forces

Kinesin-1 is a robust motor that carries intracellular cargos towards the
plus ends of microtubules. However, optical trapping studies reported that
kinesin-1 is a slippery motor that quickly detaches from the microtubule,
and multiple kinesins are incapable of teaming up to generate large
collective forces. This may be due to the vertical (z) forces that the
motor experiences in a single bead trapping assay, accelerating the
detachment of the motor from a microtubule. Here, we substantially lowered
the z-force by using a long DNA handle between the motor and the trapped
bead and characterized the motility and force generation of single and
multiple kinesin-1s. Contrary to previous views, we show that kinesin-1 is
a robust motor that resists microtubule detachment before it reaches high
hindering forces, but it quickly detaches under assisting forces even at
low z-forces. We also demonstrate highly efficient collective force
generation by multiple kinesin-1 motors. These results provide an
explanation for how multiple kinesins team up to perform cellular
functions that require higher forces than a single motor can bear.