Scientists identify substance that may have sparked life on Earth

A computer rendering of the Nickelback peptide shows the backbone nitrogen atoms (blue) connecting two critical nickel atoms (orange). Scientists who have identified this part of a protein believe it may provide clues to detecting planets on the verge of producing life. Credit: The Nanda Laboratory

A team of Rutgers scientists dedicated to tracing the primordial origins of metabolism—a core set of chemical reactions that first fueled life on Earth—has identified part of a protein that could give scientists clues to spotting planets on the verge of producing life.

The research, published in Advances in Sciencehas important implications for the search for extraterrestrial life because it gives researchers a new idea 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 candidates for the chemical that started life was a simple peptide with two nickel atoms that they call “Nickelback” not because of the Canadian rock band, but because nitrogen of its backbone atoms connect two critical nickel atoms. A peptide is a component of a protein made up of a few basic building blocks known as amino acids.

“Scientists believe that somewhere between 3.5 and 3.8 billion years ago, there was a tipping point, which started the change from prebiotic chemistry – molecules before life – to living, biological systems,” Nanda said. “We think the change was triggered 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’.”

The scientists conducting the study are part of a Rutgers-led group called Evolution of Nanomachines in Geospheres and Microbial Ancestors (ENIGMA), which is part of NASA’s Astrobiology program. Researchers seek to understand how proteins evolved to become the dominant catalyst of life on Earth.

Scientists identify substance that may have sparked life on Earth

NB structure model and comparison with natural enzymes. [Ni-Fe] Hydrogenase (left) (PDB ID: 5XLE) and ACS (right) (PDB ID: 1RU3) are large, complex proteins with bimetal active sites coordinated by a few ligands. The model structure of NB (middle) combines elements of both active sites in a 13-residue polypeptide. Credit: Advances in Science (2023). DOI: 10.1126/sciadv.abq1990

When scanning the universe with telescopes and probes for signs of past, present or emerging life, NASA scientists look for specific “biological signatures” known to be harbingers of life. Peptides like nickelback could become the latest biosignature NASA uses to detect planets on the verge of producing life, Nanda said.

A prototypical trigger chemical, the researchers argued, would have to be simple enough to be self-assembled into a prebiotic soup. But it would have to be sufficiently chemically active to be able to take energy from the environment to drive a biochemical process.

To do this, the researchers took a “reductive” approach: They started by looking at existing modern proteins known to be associated with metabolic processes. Knowing that proteins were too complex to have appeared early, they built them into their basic structure.

After a series of experiments, the researchers concluded that the best candidate was Nickelback. The peptide consists of 13 amino acids and binds two nickel ions.

Nickel, they reasoned, was an abundant metal in the early oceans. When attached to the peptide, the nickel atoms become powerful catalysts, attracting extra protons and electrons and producing hydrogen gas. Hydrogen, the researchers argued, was also more abundant on the early Earth and would have been a critical energy source for boosting metabolism.

“This is important because while there are many theories about the origin of life, there are very few actual laboratory tests of these ideas,” Nanda said. “This work shows that, not only are simple protein-metabolizing enzymes possible, they are also very stable and very active – making them a plausible starting point for life.”

More information:
Jennifer Timm et al, Design of a Minimal Di-Nickel Hydrogenase Peptide, Advances in Science (2023). DOI: 10.1126/sciadv.abq1990. www.science.org/doi/10.1126/sciadv.abq1990

Provided by Rutgers University

Reference: Scientists identify substance that may have sparked life on Earth (2023, March 10) Retrieved March 11, 2023, from https://phys.org/news/2023-03-scientists-substance-life-earth.html

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