Grand Prismatic Spring, the largest hot spring at Yellowstone National Park in the US. Credit: Frank Kovalchek (CC BY)
Chemists have shown how ribonucleic acid (RNA) and amino acids can spontaneously come together to synthesise proteins, a key component of life, in conditions which could have occurred on early Earth.
The findings provide new clues to how life may have first emerged billions of years ago.
“There are numerous problems to overcome before we can fully elucidate the origin of life, but the most challenging and exciting remains the origins of protein synthesis,” says Matthew Powner, a professor at University College London (UCL), UK, and senior author of the study.
“Life relies on the ability to synthesise proteins – they are life’s key functional molecules.
“Life today uses an immensely complex molecular machine, the ribosome, to synthesise proteins.
“This machine requires chemical instructions written in messenger RNA, which carries a gene’s sequence from a cell’s DNA to the ribosome.
“The ribosome then, like a factory assembly line, reads this RNA and links together amino acids, one by one, to create a protein.
“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. The chemistry is spontaneous, selective and could have occurred on the early Earth.”
This process of amino acid activation began with amino acids reacting with a sulphur-bearing compound called pantetheine to form thioesters – a high-energy compound involved in many biochemical processes.
“Our study unites 2 prominent origin-of-life theories – the ‘RNA world’, where self-replicating RNA is proposed to be fundamental, and the ‘thioester world’, in which thioesters are seen as the energy source for the earliest forms of life,” explains Powner.
Next, they showed that RNA sequences could spontaneously bind to specific amino acids to synthesise peptides without the need for a ribosome.
Lead author Dr Jyoti Singh, also from UCL Chemistry, says their study demonstrates how 2 primordial chemical LEGO pieces (activated amino acids and RNA) could have built peptides, short chains of amino acids that are essential to life.
In this way, RNA on an ancient Earth could have begun to encode instructions for protein synthesis.
“What is particularly groundbreaking is that the activated amino acid used in this study is a thioester, a type of molecule made from Coenzyme A, a chemical found in all living cells. This discovery could potentially link metabolism, the genetic code and protein building.”