“Of primary importance:” no other component of your diet boasts that etymology, but then the other aspects of the Canada Food Guide just aren’t as essential as protein when it comes to maintaining a healthy cell life. Though DNA often steals the limelight, proteins are among those basic building blocks of life, and participate in every activity within a cell. So when U of T chemistry professor Ronald Kluger and his team announced in late December that they had found a way to develop proteins not found in nature, it opened the door, many thought, to creating whole new forms of life without genetic mutation.
The science isn’t anywhere near that stage of development yet—the researchers have not finished perfecting their process for developing these molecules, let alone moved on to creating new organisms. Still, the discovery has exiting potential. Currently, there are about 20 amino acids that can be combined to form a protein. “It’s the equivalent of cooking with 20 ingredients,” says Kluger. “Just think how much more creative you can be if you had other possibilities.”
Protein synthesis occurs in the ribosomes of a cell, and depends on the function of two molecules: messenger RNA (mRNA), which carries the coding for a protein from DNA’s genetic template, and transfer RNA (tRNA), which aligns with mRNA according to the genetic code. Transfer RNA carries an amino acid at one end, and proteins are formed from a series of these molecules. The research housed at U of T’s Lash Miller Chemistry Laboratories focused on a synthetic replacement for the enzyme—synthetase— that binds an amino acid to tRNA. Using lanthanum salts as a replacement, this new process theoretically frees protein production from the determinism of the genetic blueprint.
Kluger and his team aren’t the first to try to change the end result of RNA transfer, but they’ve been the most successful in offering a viable method. They’ve done it chemically, to boot. Traditionally, researchers have attempted to find biological solutions: using E. coli bacteria, for example, to mutate tRNA synthetase, and make it more tolerant to different amino acids. “All of the exciting people in the field had been working on it for 20 years, and had tried completely different approaches—nothing like this,” says Kluger. Though other researchers had come up with chemical processes, they were highly impractical because they were difficult to repeat, let alone use for further research.
Kluger is respectful of these earlier discoveries, but skeptical of their usefulness: “It’s about five to 10 steps—difficult steps. The people who were doing it were the top people in the world for this kind of stuff and, practically, it was too hard for anyone to do, so although they were able to report that they’d done it, and it was going to lead to all these things […] they’d never make enough [protein] by doing them.”
What amazes Kluger is in all the attempts to modify the natural process of protein synthesis, few thought to emulate it. “If nature does this […] why can’t I make that kind of a thing do this kind of reaction? No one had ever done that, and it never occurred to anybody that you could.” Biomimetics set the research agenda.
Biomimetics is the modification of methods found in nature to create new technologies. A classic example of biomimicry is the invention of Velcro, which occurred in 1948 when Swiss engineer George de Mestral was cleaning burrs out of his dog’s long hair. Kluger found inspiration in another example, provided by notable Columbia chemistry professor Ronald Breslow. “We did not simply make larger versions of birds in inventing airplanes, but we did take the ideas, the wings from nature,” Breslow once said. “The goal of biomimetic chemistry is a large one—learn how to imitate the chemistry of life using our own new chemistry. That will not have been completely reached until we can make cells that have at least some of the properties of life itself.”
“This is what nature does,” Kluger says, pointing at a diagram of aminoacylation as it occurs in nature. “This is what we want to do,” he says, pointing out another diagram, almost identical, but for the process being controlled by himself through the production of a synthetic enzyme. With a Discovery Grant from the Natural Sciences and Engineering Research Council of Canada, Kluger and the students who work with him made a series of small discoveries, each one leading to the results published recently in the Journal of the American Chemical Society.
It was important to Kluger that the team find a process beautiful in its simplicity. No 10 steps, no biological mutations. “Mix the right chemicals together and it will work,” was the mantra. “In nature I saw that all I have to do is bring things together […] the enzymes don’t have to work very hard. So it seemed to me that this must be inherently the right thing to do. We shouldn’t be getting too artificial here.”
Easier said than found. The first challenge was in finding a compound that would bond both to an amino acid and tRNA, but that would also— and this was the hard part—do so in water, as the amino acid, synthetic enzyme, and tRNA would be brought together in an aqueous solution. Another hurdle was simply proving that the synthetic replacement worked equally well as the naturally-produced enzyme in binding amino acids to tRNA.
Synthetic protein synthesis is a careful balance between what might be considered natural and what is artificial. To those who find something ominous in the potential to build proteins not found in nature, Kluger counters that his system is better than the alternatives. “In a way it’s better than making mutants, because that would be sloppy. If they’re sloppy on one thing, they’ll be sloppy on something else.”
But then, says Kluger, “We were trying to avoid the thing that nature is really good at.” It’s a counterintuitive statement coming from someone who has just explained to me the biological precedent for the jumbo jet. But ultimately, the problem Kluger has overcome is the specificity of RNA: its editing system whereby the genetic code determines the corresponding amino acid. Kluger’s success has been the extent to which he has been able to choose which naturally-occurring elements of RNA to use, and which to only mimic. He keeps the essential structure, which makes the protein itself. He scraps the editing system. “I’m saying I want to avoid all that specificity and overcome it, so I’m doing the opposite of nature, and being totally unnatural. The goal was to avoid mimicking that aspect. We can selectively emulate nature.”
