Tumbleweed: an artificial motor protein that walks along a DNA track

Nature has used proteins to evolve molecular motors that facilitate life. Although small-molecule- and DNA-based molecular motors have been synthesized, the creation of an artificial motor protein has remained a goal of synthetic biology. Here we describe a modular approach to create an artificial motor protein, the Tumbleweed (TW). TW has three legs, each with a ligand-gated DNA binding domain that controls binding to a DNA track. TW works via a Brownian ratchet mechanism where steps are effected by diffusion and then rectified by the controlling ligands. Using single-molecule fluorescence assays and a microfluidic device, we show that TW steps directionally along a DNA track when the ligand concentrations are altered in sequence.