Building molecular motors – one step at a time

This is the movement of thousands of nanomotors, each moving independently, on a confined track. The nanomotors start at the centre, and randomly chooses a direction. The two modes moving left and right illustrate how the nanomotors begin by randomly choosing a direction and continue moving in that direction. The colour of each dot represents the number of each motor at that position in time. 

September 26, 2018
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Inside every human are trillions of cells, each containing hundreds of thousands of protein nanomotors.

These tiny protein nanomotors are ten thousand times smaller than the width of the rings in a fingerprint. Described as the ‘workhorses’ of the cell, they push and pull cargo throughout our cells.

Chapin Korosec, who is completing a PhD in physics, explains that “Nanomotors cannot simply move around randomly if they are required to perform a task — they must move in the general direction towards their intended cellular target.”

Past studies have detailed how some nanomotors move and operate, but no scientist has ever been able to create a synthetic protein-based nanomotor.

Why is this so important?

Korosec says, “These are beautifully complicated machines and engineering artificial systems will help us understand their biological counterparts." He adds, “Only then can we start thinking about how we can copy nature to create new bio-technologies.”

The field of synthetic nanoscale machinery is still in its infancy, but Korosec has made headway in understanding the physics of one of these machines.

He and his team study a class of nanomotors that are critical for plasmid separation in bacteria and collagen processing in humans. These nanomotors operate by destroying track binding sites as they move forward, thereby preventing backwards motion.

 “We developed simulations that explored a simple ‘stripped down’ model system to investigate how its physical parameters impact its performance” says Korosec. “Imagine moving through a mosh pit, with hundreds of people jostling you about” he says.  “The nanomotor we studied navigate through similarly harsh cellular environments — by moving forward they are preventing steps in reverse.”

The team found that nanomotors that move by destroying their track sites can maintain the most directional trajectories if they have many options to bind onto their track. For example,  each nanomotor has a varying number of legs that assist in locomotion.  Korosec found that increasing the number of legs, while keeping their length short, produced the most directional trajectory.

Korosec hopes that a better understanding of nanomotors may help guide treatment for diseases like osteoarthritis, rheumatoid arthritis, and osteoporosis.

 “These diseases involve the destruction of cartilage or bone due to the misregulation of proteins called MMPs.” He adds, “These delinquent MMPs destroy tissue faster than they can be repaired. If we knew what the physical mechanisms were behind proteins like MMPs, then we’d be one step closer towards understanding these diseases.”

Co-author Nancy Forde, professor of physics at SFU says, “It is important that we test our understanding of the operational principles of protein motors.  By challenging ourselves to explain and predict their behaviour, using model systems such as this one, we can determine whether we truly understand the basis of their function.”

Click here to read the study in Physical Review E.