Exceptional error minimization in putative primordial genetic codes

TL;DR

This study shows that primordial genetic codes with 16 supercodons and 10 amino acids were nearly optimal in minimizing translation errors, suggesting early selection or chance shaped their robustness.

Contribution

It demonstrates that putative primordial codes with two-letter codons and 10 amino acids were nearly optimal for error minimization, highlighting early evolutionary pressures or chance events.

Findings

Primordial codes with 16 supercodons are nearly optimal in error minimization.

Codes encoding 10 amino acids show high robustness to mistranslation.

Error minimization likely influenced early genetic code evolution.

Abstract

We investigated the error-minimization properties of putative primordial codes that consisted of 16 supercodons, with the third base being completely redundant, using a previously derived cost function and the error minimization percentage as the measure of a code's robustness to mistranslation. It is shown that, when the 16-supercodon table is populated with 10 putative primordial amino acids, inferred from the results of abiotic synthesis experiments and other evidence independent of the code evolution, and with minimal assumptions used to assign the remaining supercodons, the resulting 2-letter codes are nearly optimal in terms of the error minimization level. The results of the computational experiments with putative primordial genetic codes that contained only two meaningful letters in all codons and encoded 10 to 16 amino acids indicate that such codes are likely to have been nearly optimal with respect to the minimization of translation errors. This near-optimality could be the outcome of extensive early selection during the co-evolution of the code with the primordial, error-prone translation system, or a result of a unique, accidental event. Under this hypothesis, the subsequent expansion of the code resulted in a decrease of the error minimization level that became sustainable owing to the evolution of a high-fidelity translation system.