Kinesin-1 motility traced by an activity-based precipitating dye

Kinesin-1 is a processive motor protein that uses ATP-derived energy to transport a variety of intracellular cargoes toward the cell periphery. As tracks for cargo delivery, kinesin-1 uses a subset of microtubules within the dense microtubule network. It is still debated what defines the specific binding of kinesin-1 to a subset of microtubules. Therefore, the ability to visualize and monitor kinesin transport in live cells is critical to study the myriad of functions associated with cargo trafficking. Herein we report the discovery of a fluorogenic small molecule substrate for kinesin-1 that yields a precipitating dye. The activity of kinesin-1 thus leaves a fluorescent trail along its walking path and can be visualized without loss of signal due to diffusion. Kinesin-1 specific transport of cargo from the Golgi appears as trails of fluorescence over time.