Self-instructed condensation of amino acids and the origin of biological information

Abstract

In contemporary cells biological information is largely stored in nucleic acids. Therefore, a prerequisite in many theories on the origin of cellular life is the pre-existence of self-replicating polynucleotides that had to be formed by abiotic processes on the prebiotic Earth. It is usually assumed that the spontaneous synthesis of a self-replicating polynucleotide could take place readily. However, serious stereochemical obstacles exist which make such a synthesis extremely improbable. Amino acids, on the other hand, which are abundantly formed in prebiotic simulation experiments, are relatively easily polymerized to macromolecules (protoproteins) that share with modern proteins many properties: e.g., definable nonrandom structure, selected amino acid sequences, enzymelike activities, and self-assembly into supramolecular structures. Prebiotic polyamino acids are therefore regarded as the first informational macromolecules. The origin of this information is the chemical reactivity of the various prebiotic amino acids and their chemical response to their environment. The first informational polynucleotides were likely formed by a polynucleotide polymerase activity of prebiotic protoproteins. A comtemporary model for this process is seen, e.g., in the activity of template-free QB-replicase.