A model of the early RNA world is proposed. Nearly self-complementary sequences that could adopt double-stranded, smallhairpin-like (shRNA), structures would be selected for due to their greater hydrolytic stability. These would be phosphorylated attheir 5' ends. We suppose that dehydrating conditions arise (perhaps intermittently) in the early environment allowing amino acidsto condense with these RNA molecules. The resulting phosphate-amino acid anhydrides would play the role of early, charged,tRNAs. A crude genetic code could emerge owing to the greater resistance of some amino acid-shRNA pairings to hydrolysisrelative to others. Early on there is no division of labor between mRNAs and tRNAs; the same molecules perform both functions.But the first systems would have encoded little in the way of protein sequence information. Rather they would have served as catalysts for the random polymerization of amino acids. It is speculated that the selective advantage inhering in such systems lay intheir ability to supply raw materials for the formation of coacervates within which the various molecules essential to proto-lifecould be concentrated. This would greatly facilitate the necessary chemistries. The evolution of homochiral protein and RNA populations is discussed. An appealing feature of this model is its ability to explain the transition from phosphorylated amino acids to the 3' ester-linked aminoacyl-tRNAs employed by modern life.
Keywords:
Subject: Biology and Life Sciences - Biochemistry and Molecular Biology
Copyright: This open access article is published under a Creative Commons CC BY 4.0 license, which permit the free download, distribution, and reuse, provided that the author and preprint are cited in any reuse.
Preprints.org is a free preprint server supported by MDPI in Basel, Switzerland.