A system of two polymerases--a model for the origin of life

Orig Life Evol Biosph. 2000 Oct;30(5):459-66. doi: 10.1023/a:1006672126867.


What was the first living molecule--RNA or protein? This question embodies the major disagreement in studies on the origin of life. The fact that in contemporary cells RNA polymerase is a protein and peptidyl transferase consists of RNA suggests the existence of a mutual catalytic dependence between these two kinds of biopolymers. I suggest that this dependence is a 'frozen accident', a remnant from the first living system. This system is proposed to be a combination of an RNA molecule capable of catalyzing amino acid polymerization and the resulting protein functioning as an RNA-dependent RNA polymerase. The specificity of the protein synthesis is thought to be achieved by the composition of the surrounding medium and the specificity of the RNA synthesis--by Watson-Crick base pairing. Despite its apparent simplicity, the system possesses a great potential to evolve into a primitive ribosome and further to life, as it is seen today. This model provides a possible explanation for the origin of the interaction between nucleic acids and protein. Based on the suggested system, I propose a new definition of life as a system of nucleic acid and protein polymerases with a constant supply of monomers, energy and protection.

MeSH terms

  • DNA-Directed RNA Polymerases / metabolism*
  • Evolution, Molecular*
  • Models, Genetic
  • Origin of Life*
  • Proteins / genetics*
  • RNA / genetics*
  • RNA-Dependent RNA Polymerase / metabolism


  • Proteins
  • RNA
  • RNA-Dependent RNA Polymerase
  • DNA-Directed RNA Polymerases