The new ability of scientists to create these components could lead to the construction of completely new and useful materials, unique in their kind – ScienceDaily

These were constructed from identical protein subunits that spontaneously assemble to form long son-like helical structures.

In the natural world, protein filaments are essential components of many structural and mobile parts of living cells, as well as many body tissues.

These include the cytoskeletons that give cells their shape, the cell microtubules that orchestrate cell division and the most common protein in our body, collagen, which gives strength and flexibility to our cartilage, skin and other tissues.

"Being able to create protein filaments from scratch – or de novo – will help us better understand the structure and mechanisms of natural protein filaments and will also enable us to create entirely new, unique materials," said David Baker. Professor of Biochemistry at the University of Washington School of Medicine and Director of the UW Institute for Protein Design, who led the project. He is also a researcher at the Howard Hughes Medical Institute,

Such materials could include synthetic or artificial fibers equivalent to or greater than the resistance of spider silk, which is stronger in weight than steel, said Baker. He also mentioned the possibility of nanoscale circuits.

To design the filaments, the researchers used a computer program developed by the Baker Lab, called Rosetta, that can predict the form of a protein from its amino acid sequence.

To function properly, proteins must fold to give a precise shape. This refolding depends on the properties of the different amino acids and how they interact with each other and with the surrounding fluid environment. The attraction and repulsion forces cause the protein to settle in a form with the lowest energy level.

By calculating which form would balance these forces of attraction and repulsion to obtain the lowest total energy level, Rosetta can predict, with a high degree of accuracy, the shape that is most likely to occur. a protein will take in nature.

Using Rosetta, researchers decided to design small proteins with amino acids on their surface that would cause them to get stuck together. This allowed them to assemble into a propeller by lining up like steps in a spiral staircase. For the helix to be stable, the designed protein binds other copies positioned above and below it when the helix winds up, layer by layer.

"We were finally able to design proteins that would assemble as legos," said Hao Shen, Ph.D. candidate at the UW Molecular Engineering & Sciences Institute. He and Jorge Fallas, an acting biochemistry instructor at the UW School of Medicine, are the lead authors of an article describing this approach.

This article will be published online by the journal Science on Thursday, November 8, 2018.

Fallas said the designed proteins are relatively small. They are composed of about 180 to 200 amino acids and measure only about a nanometer long, but assemble into stable filaments of more than 10,000 nanometers long. A nanometer is 1 billionth of a meter, about the width of 10 atoms of hydrogen aligned side by side.

The researchers also showed that by altering the concentration of the protein designed in solution and adding stoppers preventing the design from binding, they could lead to growth or disassembly of the filaments.

"The ability to program the dynamics of filament formation will give us an idea of ​​how the assembly and disassembly of filaments are regulated in nature," Baker said. "The stability of these proteins suggests that they could serve as easily modifiable scaffolds for a range of applications ranging from new diagnostic tests to nanoelectronics."