Scientists have engineered a tethered ribosome that works nearly as well as the real thing—an organelle that produces all the proteins and enzymes within the cell.
Researchers may be able to manipulate the human-made ribosome in the laboratory to do things natural ribosomes cannot. This could lead to the production of new drugs and next-generation biomaterials and to a better understanding of how ribosomes function.
Called Ribo-T, the artificial ribosome was created in the laboratories of Michael Jewett, assistant professor of chemical and biological engineering in the Northwestern University McCormick School of Engineering and Applied Science, and Alexander Mankin, director of the University of Illinois at Chicago College of Pharmacy’s Center for Biomolecular Sciences.
When the cell makes a protein, mRNA (messenger RNA) is copied from DNA. The ribosomes’ two subunits, one large and one small, unite on mRNA to form the functional unit that assembles the protein in a process called translation.
Once the protein molecule is complete, the ribosome subunits—both of which are themselves made up of RNA and protein—separate from each other.
Subunits don’t separate
In a new study in Nature, the researchers describe the design and properties of Ribo-T, a ribosome with subunits that will not separate. Ribo-T may be able to be tuned to produce unique and functional polymers for exploring ribosome functions or producing designer therapeutics—and, eventually, perhaps even non-biological polymers.
No one has ever developed something of this nature.
“We felt like there was a small—very small—chance Ribo-T could work, but we did not really know,” Mankin says.
Mankin, Jewett, and their colleagues were frustrated in their investigations by the ribosomes’ subunits falling apart and coming together in every cycle of protein synthesis. Could the subunits be permanently linked together? The researchers devised a novel designer ribosome with tethered subunits: Ribo-T.
“What we were ultimately able to do was show that by creating an engineered ribosome where the ribosomal RNA is shared between the two subunits and linked by these small tethers, we could actually create a dual translation system,” Jewett says.
“It was surprising that our hybrid chimeric RNA could support assembly of a functional ribosome in the cell. It was also surprising that this tethered ribosome could support growth in the absence of wild-type ribosomes,” he says.
Keeping cells alive
Ribo-T worked even better than Mankin and Jewett believed it could. Not only did Ribo-T make proteins in a test tube, but it also was able to make enough protein in bacterial cells that lacked natural ribosomes to keep the bacteria alive.
This surprised Jewett and Mankin. Scientists had previously believed that the ability of the two ribosomal subunits to separate was required for protein synthesis.
“Obviously this assumption was incorrect,” Jewett says.
“Our new protein-making factory holds promise to expand the genetic code in a unique and transformative way, providing exciting opportunities for synthetic biology and biomolecular engineering,” Jewett says.
“This is an exciting tool to explore ribosomal functions by experimenting with the most critical parts of the protein synthesis machine, which previously were ‘untouchable,'” Mankin adds.
The Defense Advanced Research Projects Agency (DARPA), the National Science Foundation, and the David and Lucille Packard Foundation Fellowship supported the work.
Sam Hostettler at the University of Illinois at Chicago contributed to writing of this release.
Source: Northwestern University