  Theoretical analysis, which maps single molecule time trajectories of a
molecular motor onto unicyclic Markov processes, allows us to evaluate the heat
dissipated from the motor and to elucidate its dependence on the mean velocity
and diffusivity. Unlike passive Brownian particles in equilibrium, the velocity
and diffusion constant of molecular motors are closely inter-related to each
other. In particular, our study makes it clear that the increase of diffusivity
with the heat production is a natural outcome of active particles, which is
reminiscent of the recent experimental premise that the diffusion of an
exothermic enzyme is enhanced by the heat released from its own catalytic
turnover. Compared with freely diffusing exothermic enzymes, kinesin-1 whose
dynamics is confined on one-dimensional tracks is highly efficient in
transforming conformational fluctuations into a locally directed motion, thus
displaying a significantly higher enhancement in diffusivity with its turnover
rate. Putting molecular motors and freely diffusing enzymes on an equal
footing, our study offers thermodynamic basis to understand the heat enhanced
self-diffusion of exothermic enzymes.

Subcellular Processes;Statistical Mechanics;Biological Physics;Biomolecules