SCIENTISTS have recreated a key step that could have set life in motion nearly 4 billion years ago, showing how amino acids — the building blocks of proteins — can spontaneously attach to RNA under conditions plausible on the early Earth. Researchers at UCL report in Nature that they were able to link amino acids to RNA. Until now, efforts dating back to the early 1970s had been unable to accomplish this under realistic conditions similar to what could be on the early Earth. Proteins perform most of life’s functions, but they cannot replicate themselves or encode instructions for their own production. Those instructions come from RNA, a molecule related to DNA. Today, cells use an enormously complex molecular machine, the ribosome, to read messenger RNA and assemble amino acids into proteins. The UCL team has demonstrated the first, simpler part of that process: attaching amino acids to RNA in a spontaneous and selective reaction that could have occurred on the primitive Earth. The breakthrough relies on activating amino acids as thioesters, high?energy compounds long suspected to have played a role in early biochemistry. The researchers converted amino acids into thioesters using pantetheine, a sulfur?bearing compound the team previously showed can form under early Earth?like conditions. Earlier attempts used highly reactive reagents that broke down in water or caused amino acids to react with each other rather than with RNA. “We have achieved the first part of that complex process, using very simple chemistry in water at neutral pH to link amino acids to RNA,” said Professor Matthew Powner of UCL’s Department of Chemistry. “The chemistry is spontaneous, selective, and could have occurred on the early Earth.” He added that the work helps unite two origin?of?life ideas: the “RNA world,” in which self?replicating RNA was central, and the “thioester world,” in which thioesters supplied early biochemical energy. Lead author Dr. Jyoti Singh said the findings bring researchers closer to the goal of assembling life’s basic components from simple molecules. “Our study shows how two primordial chemical LEGO pieces — activated amino acids and RNA — could have built peptides, short chains of amino acids essential to life,” Singh said. She noted that the activated amino acids used are thioesters related to Coenzyme A, a molecule found in all living cells, which could link metabolism, the genetic code and protein assembly. The next challenge is to show how specific RNA sequences could bind particular amino acids, allowing RNA to start encoding instructions for proteins — the origin of the genetic code. The team also said the reactions they demonstrated are more likely to have occurred in concentrated settings such as pools or lakes rather than the open ocean, where key chemicals would have been too diluted. The reactions are too small to see with a visible-light microscope and were tracked using a range of techniques that are used to probe the structure of molecules, including several types of magnetic resonance imaging and mass spectrometry. (SD-Agencies) | 