Evolution of an Enzyme from a Noncatalytic Nucleic Acid Sequence
Life as we know it requires thousands of biological molecules, called enzymes, which carry out chemical reactions and allow life to exist. These molecules did not appear out of thin air – they evolved out of a mixture of the Earth’s first compounds, known as prebiotic soup. One theory for how life originated is known as the “RNA World” Hypothesis: ribonucleic acid (RNA), capable of both encoding information and performing enzymatic reactions, could have been the initiator of the origins of life, bridging the gap between life and non-life.
In this project, we used a sequence of DNA as a proxy for RNA in the origins of life. Wesubjected it to a process called in vitro selection, where we randomly introduced small variations in the sequence and then obliged the sequences to carry out a reaction. The sequences were filtered – only sequences able to perform the specific reaction were permitted to survive. These unique sequences were then subjected to cycles of this process – induction of small variations, and segregation of competent sequences. Using this method, we were able to take a sequence which was incapable of an enzyme-like reaction, and evolve it with minimal changes into a sequence adept at executing the reaction. This experiment allows us a tiny peep into how RNA molecules could have acquired function at the brink of the origin of life.