Noise-induced acceleration of single molecule kinesin-1

Fluctuations are ubiquitous and prominent in microscopic systems. Observations in vitro have confirmed motor proteins are subjected to thermal fluctuations. The walking molecular motor, kinesin-1 (hereafter called kinesin), which carries vesicles on microtubules in cells, has long been proposed to utilize thermal fluctuations to make directed movements. In addition to thermal fluctuations, living cells actively generate non-thermal fluctuations using energy derived from metabolic activities. However, it is not clear whether and how these active fluctuations affect the function of kinesins in living cells. To investigate the effect of active fluctuations on single kinesin molecules, we used an in vitro measurement system to apply actively fluctuating external forces (i.e. noise), artificially mimicking intracellular active fluctuations. Here we show that kinesin accelerates in response to the applied noise, especially under the application of a large average hindering force (load). The acceleration was quantitatively explained with a mathematical model using independently determined parameters. The universality of the theory behind the model suggests that intracellular enzymes share a similar noise-induced acceleration mechanism, meaning that the active fluctuations in cells are not just noise but utilized to improve the activity of biomolecules.