Scientists think they discovered the origin of life on Earth

Life needs proteins for almost everything, from cell repair to immune defense. Scientists have long asked how the first proteins were formed before cells had complex machinery.

A new study reports a simple, water-friendly reaction that links early ingredients into the first steps toward protein-making.

The project was led by Professor Matthew Powner at University College London (UCL), a chemist whose lab explores prebiotic chemistry.

“At life’s functional core, there is a complex and inseparable interplay between nucleic acids and proteins, but the origin of this relationship remains a mystery,” wrote the researchers.

Molecules that build proteins

The team showed that RNA – a molecule that stores and transfers genetic information and can catalyze reactions – can become chemically linked to amino acids.

These small molecules build proteins, and the linkage occurs under mild conditions in water.

The researchers changed amino acids into a more reactive form that holds extra energy, then linked those energized amino acids to RNA at a specific spot in the molecule, all without needing enzymes.

The reaction preferred the end of a double stranded RNA over interior positions, which avoids random chemistry that would scramble sequences.

The experts also reported strong yields for several amino acids, including arginine linked to adenosine at up to 76 percent.

Sulfur chemistry drives origins

A thiol is a sulfur-containing compound common in metabolism, and thioesters made from thiols power many reactions in modern cells.

Using thioesters makes chemical sense for early Earth because they react in water without falling apart quickly, helping drive protein-related chemistry.

Earlier work from the same community showed that pantetheine, the active fragment of Coenzyme A that forms many biological thioesters today, can form under prebiotic conditions in water.

That work supports the idea that the same types of sulfur chemistry existed before life began.

This new result connects that energy-rich chemistry to RNA handling of amino acids. It links metabolism- like reactions to information carriers, which is exactly the bridge origin of life research has needed.

Molecules found in all living cells

The team uncovered a switch that controls two different steps. In step one, thioesters favor attaching the amino acid to RNA, creating aminoacyl RNA in water at neutral pH.

In step two, converting to thioacids and adding a mild oxidant pushed peptide bond formation, which produced peptidyl RNA in very high yields.

Peptides are short chains of amino acids, usually two to 50 units long, while larger folded chains are proteins.

Making peptidyl RNA shows that RNA-bound amino acids can be extended into short chains, a necessary move toward protein-like function.

“What is 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,” said Dr. Jyoti Singh of UCL Chemistry. “This discovery could potentially link metabolism, the genetic code, and protein building,”

Neutral waters spark proteins

The chemistry works in water at near neutral pH, which points to pools, lakes, or wet shorelines rather than the open ocean.

Concentrations would have been higher in small bodies of water, and minerals could have helped organize the molecules.

Freeze concentrate cycles also help. The researchers observed effective aminoacylation under eutectic ice conditions near 19°F.

In this environment, ice excludes salt and concentrates solutes into brines, which speed reactions without harsh reagents.

“It seems pretty probable that this reaction would have been occurring on early Earth,” said Professor Powner. That assessment reflects the mild requirements and the water compatibility of the chemistry.

Bridging chemistry and biology

Modern cells make proteins with the ribosome, a ribonucleoprotein machine that reads messenger RNA and couples amino acids with the help of transfer RNAs.

The new chemistry provides a path for RNA to handle amino acids without proteins, easing the chicken or egg problem.

An earlier study proposed an RNA peptide world in which RNA and short peptides co-evolved, forming chimeric molecules that could grow and select function.

The present result shows a plausible way for RNA to acquire and extend amino acids in water.

The modern genetic code

The genetic code is the set of rules that maps RNA triplets to amino acids.

By preferring attachment at RNA termini and operating under duplex control, this chemistry hints at how sequence specific pairing could later become coded instruction.

The researchers point to the need for sequence preferences that pair specific RNA sequences with specific amino acids. That would move from chemistry that charges RNA to chemistry that begins to encode.

Success there would show how early RNA could use simple rules to shape peptide sequences, with later evolution building the fully fledged ribosome and the modern code.

The study is published in the journal Nature.

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