The Tumbleweed: construction of a synthetic protein motor

Davies R1, Bromley E2, Niman C3, Blab G4, Woolfson D5, Zuckermann M6, Forde N6, Linke H3 and Curmi P1

  1. School of Physics, UNSW Sydney, Australia.
  2. Department of Physics, University of Durham, UK.
  3. Solid State Physics and Nanometer Structure Consortium, Lund University, Sweden.
  4. Molecular Biophysics, Universiteit Utrecht, The Netherlands.
  5. School of Biochemistry, Bristol University, UK.
  6. Department of Physics, Simon Fraser University, Canada.

Molecular motors and machines are highly complex, multi-subunit proteins that use chemical energy to perform a multitude of critical, mechanical tasks in cells. The physical mechanisms by which motor proteins (such as myosin and kinesin) transduce chemical energy into mechanical work are still poorly understood. Traditionally, scientists have taken a “top down” approach to addressing this question by determining crystal structures of motor proteins, characterizing mutants and making single molecule measurements of performance. The goal of our work is to take a “bottom up” approach and design an artificial motor based on non-motor protein components. In this way, we can test our understanding of motor protein operation by including components that have well characterized functional properties. Our current design, the Tumbleweed, consists of a three-legged clocked-walker protein that operates on a repetitive DNA track. Tumbleweed uses three discrete ligand-dependent DNA-binding domains (repressor proteins) to perform cyclical ligand-gated rectified diffusion along a synthetic DNA molecule. We have used a modular combination of molecular biology and synthetic biology to express and assemble the Tumbleweed motor where three different DNA-binding proteins are linked to an assembly hub via coiled-coil arms. The SpyCatcher-SpyTag system was used to create the covalently linked Tumbleweed motor. We are currently assaying Tumbleweed for motion on a DNA track.