, Volume 30, Issue 5, pp 459-466

A System of Two Polymerases – A Model for the Origin of Life

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What was the first living molecule – RNA or protein?This question embodies the major disagreement instudies on the origin of life. The fact that incontemporary cells RNA polymerase is a protein andpeptidyl transferase consists of RNA suggests theexistence of a mutual catalytic dependence betweenthese two kinds of biopolymers. I suggest that thisdependence is a `frozen accident', a remnant from thefirst living system. This system is proposed to be acombination of an RNA molecule capable of catalyzingamino acid polymerization and the resulting proteinfunctioning as an RNA-dependent RNA polymerase. Thespecificity of the protein synthesis is thought to beachieved by the composition of the surrounding mediumand the specificity of the RNA synthesis – by Watson– Crick base pairing. Despite its apparent simplicity,the system possesses a great potential to evolve intoa primitive ribosome and further to life, as it isseen today. This model provides a possible explanationfor the origin of the interaction between nucleicacids and protein. Based on the suggested system, Ipropose a new definition of life as a system ofnucleic acid and protein polymerases with a constantsupply of monomers, energy and protection.