Every organism present on earth has amino acids. That is because all things on earth are connected through this tree of life to an origin, an organism that was the ancestor of all living things. A new study details the events that shaped why that ancestor got the amino acids it did.
To do this, scientists simulated early Earth conditions in the lab. They mimicked the original protein synthesis of 4 billion years ago by using an alternative set of amino acids that were very abundant before life on Earth emerged.
They found that the biochemistry of prehistoric organic compounds contained the amino acids best suited for protein folding. In other words, life on Earth evolved because some amino acids were available and easy to synthesize in prehistoric environments. Some were particularly good at helping proteins take on certain forms to carry out essential activities.
Ancient proteins wouldn’t have known how to evolve into anything alive today without specific amino acids.
Stephen Fried, a Johns Hopkins chemist who co-led the research with scientists from Charles University in the Czech Republic, said: “Folding proteins allowed us to do evolution before there was even life on our planet. You could have evolution before you had biology; you could have natural selection for the chemicals that are useful for life even before there was dna laundry.
For the first billion years, Earth’s atmosphere consisted of several gases, including ammonia and carbon dioxide, which combined with intense ultraviolet radiation to form some of the simplest classical amino acids. Others came via special delivery by meteorites, which brought a variety of components and completed a set of 10 “early” amino acids that aided life on Earth.
fried said, “We are trying to discover what was so special about our canonical amino acids. Were they selected for a particular reason?”
According to scientific estimates, the Earth is 4.6 billion years old and it was not until 3.8 billion years ago that DNA, proteins and other chemicals began to form primitive life. The latest research offers new hints at the conundrum of what happened in between.
fried said, “To have evolution in a Darwinian sense, you need this advanced way of converting genetic molecules like DNA and RNA into proteins. But for DNA to replicate, proteins are also needed, so we have a chicken-and-egg problem. Our research shows that before Darwinian evolution, nature could have chosen building blocks with useful properties.”
Amino acids have been found in asteroids far from Earth, indicating that these substances are found throughout the universe. Fried believes the new findings could also affect the chances of discovering life in space.
Fred said: “The universe seems to love amino acids. Maybe it wouldn’t be so different if we found life on another planet.”
- Mikhail Makarov, Alma C. Sanchez Rocha et al. Early selection of the amino acid alphabet was adaptively shaped by biophysical constraints of foldability. The Journal of the American Chemical Society. DOI: 10.1021/jacs.2c12987