A team of Rutgers scientists dedicated to identifying the primordial origins of metabolism–the set of essential chemical reactions that first gave rise to life on Earth–has identified a fragment of a protein that could provide clues for scientists to spot planets about to produce life.
Research published in Science advancesIt has important implications in the search for extraterrestrial life because it gives researchers a new clue to search for, said Vikas Nanda, a researcher at the Center for Advanced Biotechnology and Medicine (CABM) at Rutgers.
Based on laboratory studies, Rutgers scientists say one of the most likely chemical candidates for starting life was a simple peptide with two nickel atoms that they dub “Nickelback” not because it has nothing to do with the Canadian rock band, but because of the nitrogen that forms its backbone. . The atoms bond two critical nickel atoms. A peptide is a component of a protein that is made up of a few building blocks known as amino acids.
“Scientists believe that sometime between 3.5 and 3.8 billion years ago there was a tipping point, something that started the shift from prebiotic chemistry — molecules before life — to living biological systems,” Nanda said. “We think the change was triggered by a few small proto-proteins that performed key steps in an ancient metabolic reaction. We think we’ve found one of these ‘leader peptides.'”
The scientists who conducted the study are part of a Rutgers-led team called Evolution of Nanomachines in Geospheres and Microbial Ancestors (ENIGMA), which is part of the Astrobiology Program at NASA. Researchers seek to understand how proteins evolved to become the main enablers of life on Earth.
As NASA scientists scour the universe with telescopes and probes looking for signs of past, present, or emerging life, NASA scientists are looking for specific “biosignatures” that are known to be harbingers of life. Nanda said that peptides like Nickelback could become the latest biosignature that NASA uses to detect planets on the verge of producing life.
The researchers determined that the original trigger chemical must be simple enough to be able to spontaneously assemble into the prebiotic soup. But it must be chemically active enough to have the ability to take energy from the environment to drive a biochemical process.
To do this, the researchers adopted a “reductionist” approach: they began by examining existing proteins known to be involved in metabolic processes. Knowing that proteins were too complex to appear ahead of time, they reduced them to their basic structure.
After a series of experiments, the researchers concluded that the best candidate is Nickelback. The peptide consists of 13 amino acids and binds two nickel ions.
They believed that nickel was an abundant metal in the early oceans. When bound to the peptide, the nickel atoms become powerful catalysts that attract more protons and electrons and produce hydrogen gas. The researchers concluded that hydrogen was also more abundant on early Earth and would have been an important source of energy to boost metabolism.
“This is important because while there are many theories about life’s origins, there are very few actual laboratory tests of these ideas,” Nanda said. “This work shows that not only are simple protein-metabolizing enzymes possible, but that they are also very stable and very active — making them a plausible starting point for life.”
