Researchers from UNSW Sydney have built the first artificial protein motor capable of taking controlled, directional steps along a DNA track.

The protein, dubbed Tumbleweed, moves by alternating between three "feet" that bind to specific DNA sequences. By changing the surrounding chemical environment, the researchers can control both when the motor steps and the direction it travels.

The work, published in Nature Nanotechnology, represents a milestone in synthetic biology and nanotechnology.

“This moment culminates two decades of research by our national and international team,” says Professor Paul Curmi from UNSW.

"We’ve demonstrated that we can engineer entirely new behaviours into proteins by assembling existing biological components in new ways”.

Nature's molecular motors—including kinesin, dynein and myosin—transport cargo around cells, power muscle contraction and perform many of the mechanical tasks essential for life.

Building artificial motor proteins from the bottom-up has been a longstanding goal because it offers unique insights into how these extraordinarily complex machines work and how they might eventually be redesigned.

The team built Tumbleweed from protein modules that individually have no motor function.

Together, however, they produce a machine capable of walking along engineered DNA tracks, taking multiple 16-nanometre steps in response to externally supplied chemical signals.

The direction of movement could be reversed simply by changing the sequence of those signals.

The work establishes a new platform for studying how molecular motors function and how synthetic versions might one day be engineered for specific tasks.

“We follow the maxim of physicist Richard Feynman: ‘what I cannot create, I do not understand’,” says Professor Curmi.

“By doing this, we can learn the principles by which nanoscale protein motors achieve their remarkable characteristics and start to understand the trade-offs involved.”

“We are currently optimising Tumbleweed.  Our immediate goals are to determine how far can Tumbleweed walk (currently about 100 nanometres) and how fast can it walk (currently about 1 nanometre per second).

“Beyond this, we are working towards autonomous designs that do not need external control.”

The work provides a foundation for future generations of programmable protein nanomachines and, ultimately, autonomous synthetic molecular motors.

These may find applications such as massively-parallel biocomputation, which is energy efficient, sustainable and scalable.