Scientists may have discovered a reaction that provides the “missing link” to help explain how early life formed on Earth about 4 billion years ago.
All living things contain ribonucleic acid, otherwise known as RNA, a core molecule that serves crucial functions in organisms like decoding genetic information and helping build proteins from simpler amino acids.
However, the process of RNA attaching to amino acids, RNA aminoacylation, has never been experimentally observed in conditions matching the early Earth.
In a study published Wednesday in Nature, a team of University College London researchers describes an experiment that allowed them to link amino acids to RNA in water in a neutral PH environment reminiscent of conditions around the time life was thought to have formed on Earth.
By attaching amino acids to a sulphur-bearing chemical group called a thioester, another compound found on the early Earth, the scientists observed the molecules react spontaneously and selectively with RNA.
The natural structure of the RNA even helped guide the amino acids to the end of the RNA strand, the location where they would need to be for eventual protein synthesis.
“RNA molecules communicate information between themselves in a highly predictable and extremely effective way, but RNAs do not inherently communicate with the amino acids that they need to control in protein synthesis,” Professor Matthew Powner, a senior author of the study, told BBC Science Focus. “So how and why these two molecules first came to be linked has been an open and unresolved question for decades.”
The researchers said their work helped bridge two different theories for the origin of life on Earth, known as “RNA world” and “thioester world,” each named for the compound adherents argued first set off life-forming processes.
“What we found, which is kind of cool, is that if you put them both together, they’re more than the sum of their parts,” Powner said in a separate interview with 404 Media. “Both aspects—RNA world and thioester world—might be right and they’re not mutually exclusive. They can both work together to provide different aspects of things that are essential to building a cell.”
Previous attempts to recreate this reaction were unsuccessful, sometimes with amino acids reacting with each other rather than RNA, and other times with unstable conditions in water, causing the process to break down.
Future experiments could build on the basic reactions seen in this one, with researchers aiming to someday create self-replicating structures.
“Imagine the day that chemists might take simple, small molecules, consisting of carbon, nitrogen, hydrogen, oxygen, and sulphur atoms, and from these LEGO pieces form molecules capable of self-replication,” lead author Dr. Jyoti Singh said in a news release. “This would be a monumental step towards solving the question of life’s origin.”
“Our study brings us closer to that goal by demonstrating how two primordial chemical LEGO pieces (activated amino acids and RNA) could have built peptides, short chains of amino acids that are essential to life,” she added.
The UCL team believes the reaction they demonstrated could’ve taken place in early lakes and nutrient-rich pools.
Observers said the recent breakthrough may someday be seen as a fundamental new chapter in early-life biology.
“This team of researchers has not only achieved peptide synthesis with the participation of RNA molecules, in a manner analogous to but much simpler than that of living cells, but they have also managed to do so under neutral aqueous conditions and using a form of energy activation that is highly plausible for the first steps of life on Earth,” Kepa Ruiz Mirazo, a biophysicist and philosopher at the University of the Basque Country, told El País English, arguing the researchers’ findings could be “the most significant in recent times” in the field.
“There are still many pieces to be solved in the immense puzzle of the origin of life on our planet, but science has found a very important place to fit.”