Life on Earth, and potentially other worlds, might have started after a unique fusion of amino acids with metal ions, say NASA researchers who think they’ve found the peptide central to the earliest metabolic events.
Such ancient metabolic reactions would have been the opening acts of Earth life’s more than three-billion-year journey.
And they were probably made possible thanks to a protein fragment possessing a spine of nickel-bonded nitrogen molecules.
The peptide, dubbed ‘Nickelback’ in reference to its metal-bonded backbone, could now be used by space explorers as a marker to detect life on other planets.
A team at Rutgers University working on the NASA Astrobiology program, were hunting for molecular ‘biosignatures’ that could point to the presence of early life. They took a list of known metabolic proteins, considered their constituent structures – amino acids and peptides – and whittled these down to a sole candidate.
With its 13 amino structure binding to two nickel ions, Nickelback appears feasible as an early life biosignature, as it likely played a role in hydrogen reactions. The team believes primordial, nickel-rich oceans with water-soluble ions present in the protein, are likely to have served a role in catalysing hydrogen reactions.
While today’s complex organisms use oxygen in aerobic energy reactions, early cellular life would have relied on hydrogen in metabolic processes. When bound to the amino acid chain, the two nickel ions would have drawn protons and electrons that catalyse hydrogen.
These first reactions, says senior researcher Vikas Nanda, likely happened between 3.5 and 3.8 billion years ago, when chemistry within the early Earth shifted to reactions leading to biological systems.
“We believe the change was sparked by a few small precursor proteins that performed key steps in an ancient metabolic reaction. And we think we’ve found one of these ‘pioneer peptides’,” Nanda says.
“This is important because, while there are many theories about the origins of life, there are very few actual laboratory tests of these ideas.
“This work shows that, not only are simple protein metabolic enzymes possible, but that they are very stable and very active, making them a plausible starting point for life.”
Identifying Nickelback and its potential role in early metabolism marker marks another step towards learning why proteins are fundamental to life on our planet, and it’s hoped it will give a powerful candidate to focus on in NASA’s efforts exploring the universe for life beyond Earth.
Originally published by Cosmos as Scientists think Nickelback helped kickstart life on Earth
Matthew Agius is a science writer for Cosmos Magazine.
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