Scientists have found that the genetic code of ancient microorganisms was shaped by specific amino acids, shedding light on how life began on Earth. Ancient proteins would not have evolved into everything alive today without these amino acids. These findings offer new clues into what happened during the time between when DNA, proteins, and other molecules formed and when simple organisms began to emerge.

The researchers, co-led by Johns Hopkins University’s Stephen Fried and scientists from Charles University, simulated primordial protein synthesis from 4 billion years ago in the lab by using an alternative set of amino acids that were highly abundant before life arose on Earth. They found that life thrived on Earth because some amino acids were available and easy to make in ancient habitats and because some were especially good at helping proteins adopt specific shapes to perform crucial functions. This means that protein folding allowed evolution before biology existed, allowing for the natural selection of valuable chemicals for life before DNA.

Although the primordial Earth had hundreds of amino acids, all living things use the same 20 canonical compounds today. Science has struggled to pinpoint why these 20 amino acids are so special. Earth’s atmosphere was made up of gases like ammonia and carbon dioxide for its first billion years. These gases combined with high levels of ultraviolet radiation to make some of the simpler canonical amino acids. Others came to Earth on meteorites, which brought a variety of ingredients that helped life on Earth finish a set of 10 “early” amino acids.

The researchers are trying to answer what was so special about these 20 canonical amino acids with the new research, mainly because those space rocks brought much more than the “modern” amino acids. Since amino acids have been found in asteroids that are far from Earth, this suggests that these compounds are common in other parts of the universe, which could have implications for finding life beyond Earth.

This research has been published in the Journal of the American Chemical Society.

References

• Candanosa, R. M. (2023, February 27). ANCIENT PROTEINS OFFER NEW CLUES ABOUT ORIGINS OF LIFE ON EARTH. The Hub; Johns Hopkins University. https://hub.jhu.edu/2023/02/27/protein-origin-life/
• Makarov, M., Sanchez Rocha, A. C., Krystufek, R., Cherepashuk, I., Dzmitruk, V., Charnavets, T., Faustino, A. M., Lebl, M., Fujishima, K., Fried, S. D., & Hlouchova, K. (2023). Early Selection of the Amino Acid Alphabet Was Adaptively Shaped by Biophysical Constraints of Foldability. Journal of the American Chemical Society, jacs.2c12987. https://doi.org/10.1021/jacs.2c12987