Proteins that functioned in the first life forms four billion years ago have been built in a modern laboratory.
José Manuel Sanchez Ruíz from the University of Granada in Spain co-authored the study, published August 8 in the journal Structure, in which a group of seven researchers formed ancient proteins known as thioredoxins. These proteins are common in all life - they perform the most basic functions in cells - indicating that they were around when life first began.
The scientists mapped the DNA of life forms belonging to all three domains of life – Archaea, Eukaryota, and Bacteria – and found the point in evolutionary history at which the thioredoxins from the three groups diverged. The amino acid sequence that the three shared at this fork in evolution, the researchers concluded, must have been around before the groups became distinct - when the very first living things existed on Earth.
Most interesting are the experiments done with these original proteins. Ruiz and his team, intent on determining what kind of conditions ancient life thrived in, put the proteins through an obstacle course that imitated the conditions of earth’s oceans four billion years ago. They put the resurrected thioredoxins in an acidic environment with high temperatures and found that the proteins remained stable and could even bind to different chemicals.
Scienstists are unsure what drove the formation of these first proteins. One hypothesis is that they were extraterrestrial – the proteins arrived on earth via a meteor from Mars.
"Four billion years ago Mars was a much a safer place than Earth," Sanchez-Ruiz commented. "Maybe we have resurrected Martian proteins. Maybe the last universal common ancestor formed on Mars and transferred to Earth."
Find the study in the journal Structure.
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