The genetic code controls how organisms build proteins based on genetic indicators may be different from the sequence scientists once believed. A recent study explores the earliest stages of life and a new timeline for how to add proteins, the basis of proteins called amino acids, to the code. This sequence is a key piece in the puzzle of how life begins.
Professor Joanna Masel of the University of Arizona and colleagues have proposed a new approach to find out the order in which amino acids become part of the system in which all life produces proteins. Their research was published in the Proceedings of the National Academy of Sciences’ Science Journal, avoiding early speculation based on early chemicals. Instead, the team directly studied the protein composition of very old genetic material that can be traced back to the earliest known life forms.
Instead of relying on experiments trying to reproduce the early conditions of the Earth, Professor Marcel’s team studied ancient genetic patterns that initial organisms might share. These proteins are crucial to many life processes and provide clues about how biology worked billions of years ago. The researchers found that simpler, smaller amino acids were used first, while more complex amino acids were later. Surprisingly, types such as methylamino and cysteine, including sulfur and histidine that interact with metals, were earlier than previously thought.
Professor Masel explained: “The molecular weight of methionine and histidine is added to the code than its expected molecular weight, and then glutamine is later added to the code.” This means methionine may play a role in early energy-related processes, and the ability of histidine to help metal chemical reactions is crucial from the outset.
The findings of this study go beyond basic chemistry. They support the idea that life begins with minerals and sulfur-rich environments, such as underwater volcanic vents. These places will provide the right conditions for the chemical reaction of sulfur and metals. Professor Marcel’s team also found some signs that some older genetic systems existed before the earliest ancestors of all lives shared, suggesting that living had tried different ways to make proteins before settling down on the systems we know today.
To draw these conclusions, Professor Marcel’s team grouped protein parts into their time of production. These protein parts (called domains) are parts of proteins that do specific jobs in cells. The researchers then compared the frequency of each type of amino acid to that occur in the newer proteome. They found that, for example, glutamine might have been added to the genetic code very late, thus overturning early hypotheses. Other ancient proteins contain abnormal amounts of specific amino acids, such as tryptophan and tyrosine, which implies that older genetic arrangements may differ.
Professor Marcel’s research not only provides new perspectives on Earth’s history. It also provides possibilities for studying life outside our planet. If sulfur and metal-based amino acids are important in the early life here, they may also be signs of life in other worlds. “Our results provide an approximation of the order in which twenty amino acids are recruited,” Professor Marcel said.
Journal Reference
Wehbi S., Wheeler A., Morel B., Manepalli N., Minh BQ, Lauretta DS, Masel J. Proceedings of the National Academy of Sciences, 2024. DOI:
About the Author
Professor Joanna Marcel A theoretical biologist at the University of Arizona, she is known for her innovative work and explores how the most basic processes in life develop. Her research focuses on the origins of genetic systems, evolutionary theory and the molecular basis of early life. With a background in mathematics and evolutionary biology, she brings complex computational models into biological problems to discover patterns that make up life as we know it. Professor Masel has published extensively on the evolution of proteins to genetic robustness and the emergence of new traits. Her work has been recognized for challenging hypotheses and provides a new framework for understanding how biological systems adapt and develop over time. In addition to her academic contributions, she is also a mentor and advocate of scientific critical thinking, encouraging interdisciplinary approaches to answer the most difficult questions in biology. Her recent work on amino acid recruitment has formed a new perspective on how genetic codes are first.
