Our cells are full of tiny, specialized machines that carry out many critical and complex functions. The ribosome, for example, is used by cells to generate proteins. Researchers studying synthetic biology have been interested in using ribosomes in the creation of synthetic materials, but it has been challenging to get them to do work that isn't what they normally do. New research reported in Nature Communications can help change that. Scientists have now been able to rapidly generate ribosomes in a tube, and then select the ones that are able to carry out certain functions. The method is called ribosome synthesis and evolution (RISE).
"Ribosomes have an extraordinary capability as the protein synthesis machinery of the cell," said research leader Michael Jewett, the Walter P. Murphy Professor of Chemical and Biological Engineering and director of the Center for Synthetic Biology at Northwestern's McCormick School of Engineering. "But to synthesize proteins beyond those found in nature, we have to design and modify the ribosome to work with non-natural substrates. Developing ribosomes in vitro is an important part of that system, and we are very excited to have this new capability."
Researchers have already turned to the ribosome to help engineer biopharmaceuticals such as insulin, and they could be useful in creating new biopolymers that are not found in nature. There are limitations to the use of the ribosome, however, since it's normal function is inside of living organisms.
Jewett's team repurposed ribosomes by engineering DNA to make mutant ribosomes, to the tune of hundreds of thousands an hour. Magnetic beads then sort through them and find the ones with functions the researchers are interested in. Now, it may be much easier to create biopolymers with certain mutant ribosomes.
"We validated the RISE method by selecting highly active ribosomes that are resistant to the antibiotic clindamycin from a library of variants," Jewett said. "Our hope is that others will be able to use this platform to select for ribosomes that can carry out a new function."
The research team also mapped the ribosome's active site and determined which bases can be altered without disrupting ribosomal function. They found that 85 percent were flexible in some way and can be altered.
"It proves to us that you can change almost every nucleotide in the active site and still get a functional ribosome. This is so exciting for synthetic biology," Jewett added. "Right now, the ribosome is a chef that can only make certain meals. We want to create many chefs that can make many different cuisines. This is a huge step forward toward that vision." Jewett is featured discussing his work in the video.
"This collection of results represents a truly exciting step towards harnessing and adapting the biological cellular machinery to produce non-biological polymers," said Dawanne Poree, polymer chemistry program manager, Army Research Office, an element of US Army Combat Capabilities Development Command's Army Research Office. "If successful, this work will, in essence, bring synthetic materials into the realm of biological functions, and potentially rendering advanced, high-performance materials capable of catalysis, molecular encoding and data storage, nanoelectronics, self-healing, among many other functions."