Speaker
Description
Motor proteins are molecular machines that operate outside equilibrium to produce directed motion from chemical energy. Our understanding of how motor proteins transduce energy at the molecular scale is obscured by the complexity of natural motors. We attempt to use protein engineering and single-molecule biophysics to create minimal systems that allow us to test principles of nonequilibrium energy conversion. We recently developed Tumbleweed (TW), an artificial clocked protein walker and demonstrated it was capable of directional movement along a short DNA track.
TW takes up to 11 consecutive 17 nm steps with a 7 second step time dictated by our microfluidics. TW operates as a Brownian ratchet where steps are accomplished by diffusion and then rectified by the controlling ligands. To model how the observed behavior on a short track translates to long-range stepping we used Master equations governing the kinetics between the TW feet and the track. We predict that a TW moves at a speed of about 0.5 track periods per solution cycle, or ∼1.2 nm/s using the 21 s experimental cycle time.
We plan to analyse the stepping behaviour of TW using the framework of stochastic thermodynamics, which provides quantitative bounds linking efficiency, energy use, and fluctuations. To achieve this, we design DNA origami-based tracks that allow the performance of TW in terms of speed, accuracy, processivity to be measured at the single molecule level on a stiff extended linear track. The ambition is to directly compare these measured parameters to predictions Thermodynamic Uncertainty Relations, to establish fundamental bounds on motor performance.