Conditions Enabling the Persistence of Cooperating Synthetase, Ligase, and Mutation-Inhibitor Catalytic Polymers.

In origins-of-life research, a key challenge is to explain the emergence of polymers of sufficient length to confer the complex functions needed for genetic inheritance. Previous studies have demonstrated that prebiotic environments enabling multilevel selection can facilitate the survival of cooperating polymers such as ribozymes, which allows that complex functions undertaken today by long polymers might have originated from multiple simpler functions undertaken by shorter polymers. To further investigate this possibility, we developed a new computational model of cooperative catalytic and replicating polymer systems that avoids tracking all possible polymer sequences. This approach scales well computationally, avoiding the need to set an a priori cap on polymer length. We first validated this model by replicating key conclusions of previous studies, for example that the persistence of cooperative synthetase-ligase systems is facilitated by both intrinsic factors (shorter length, higher catalytic efficiency) and by factors that promote multilevel-selection (compartmentalization, slower diffusion). We then explored the effects of introducing a mutation inhibitor into a cooperative synthetase-ligase system. The results support the possibility that mutation inhibition could have arisen, not through the appearance of a single proofreading polymerase, but through the emergence of distinct, mutation inhibiting catalysts.