“We took individually folded proteins and used them as building blocks, then assembled them together piece by piece so that we can create tailored nanostructures.”
US researchers have found a new way to create single-chain protein nanostructures using synthetic biology and protein-assembly techniques.
In a media release, the McKelvey School of Engineering at Washington University in St. Louis (WUSTL) said that its team of scientists were inspired by the work of DNA origami to make these nanostructures.
The team created nanostructures — in the shapes of triangles and squares — using stable protein building blocks, according to the WUSTL. These protein nanostructures can endure high temperatures and harsh chemical conditions, both of which are not possible with DNA-based nanostructures. In the future, these protein nanostructures could be used to improve sensing capabilities, speeding chemical reactions, in drug delivery and other applications.
When trying to create protein nanostructures suited for particular applications, researchers typically make modifications to existing protein structures, such as virus particles. However, the shapes of nanostructures that can be made using this approach are limited to what nature provides, the WUSTL said. Now, Fuzhong Zang, associate professor of energy, environmental & chemical engineering, and members of his lab have developed a bottom-up approach to build 2D nanostructures, essentially starting from scratch.
“Building something that nature has not offered is more exciting,” Zhang said. “We took individually folded proteins and used them as building blocks, then assembled them together piece by piece so that we can create tailored nanostructures.”
The results of the work were published in Nature Communications on 25 July.
Using synthetic biology approaches, Zhang’s team first biosynthesised rod-shaped protein building blocks, similar in shape to a pencil but only 12 nanometres long.
Subsequently, they connected these building blocks together through reactive protein domains that were genetically fused to the ends of each of the rods, forming triangles with three rods and squares with four rods. These reactive protein domains are known as split inteins, which are not new to Zhang’s lab — they are the same tools that his group uses to make high-strength synthetic spider silk and synthetic replicas of the adhesive mussel foot proteins.
In both cases, these split intein groups enable the production of large proteins that make the synthetic spider silk tougher and stronger and the mussel foot proteins stickier, the WUSTL explained. In this case, they enable the construction of novel nanostructures.
Zhang’s team worked with Rohit Pappu, the Edwin H. Murty Professor of Engineering, professor of biomedical engineering and an expert in the biophysics of intrinsically disordered proteins, phase transitions and protein folding. Both Zhang and Pappu are members of the university’s Center for Science & Engineering of Living Systems (CSELS).
“Professor Pappu’s lab, specifically former postdoctoral fellow Jeong-Mo Choi, helped us understand how the protein sequence at the connections determines the flexibility of these nanostructures and helped us to predict protein sequences to better control the flexibility and geometry of nanostructures,” Zhang said. “The collaboration between my synthetic biology lab and Professor Pappu’s biophysical modelling lab has proven very productive.”
According to WUTSL, the collaboration simplified a very complex process.
“Once we understood the design strategy, the work is fairly straightforward and quite fun to do,” Zhang said. “We just controlled the different functional groups, then they controlled the shapes.”