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Evolution of Life on Earth: tRNA, Aminoacyl-tRNA Synthetases and the Genetic Code

by Lei Lei 1 and Zachary F Burton 2,*
1
Department of Biology, University of New England, Biddeford, ME 04005, USA
2
Department of Biochemistry and Molecular Biology, Michigan State University, E. Lansing, MI 48824-1319, USA
*
Author to whom correspondence should be addressed.
Life 2020, 10(3), 21; https://doi.org/10.3390/life10030021
Received: 5 January 2020 / Revised: 13 February 2020 / Accepted: 27 February 2020 / Published: 2 March 2020
(This article belongs to the Section Origin of Life)
Life on Earth and the genetic code evolved around tRNA and the tRNA anticodon. We posit that the genetic code initially evolved to synthesize polyglycine as a cross-linking agent to stabilize protocells. We posit that the initial amino acids to enter the code occupied larger sectors of the code that were then invaded by incoming amino acids. Displacements of amino acids follow selection rules. The code sectored from a glycine code to a four amino acid code to an eight amino acid code to an ~16 amino acid code to the standard 20 amino acid code with stops. The proposed patterns of code sectoring are now most apparent from patterns of aminoacyl-tRNA synthetase evolution. The Elongation Factor-Tu GTPase anticodon-codon latch that checks the accuracy of translation appears to have evolved at about the eight amino acid to ~16 amino acid stage. Before evolution of the EF-Tu latch, we posit that both the 1st and 3rd anticodon positions were wobble positions. The genetic code evolved via tRNA charging errors and via enzymatic modifications of amino acids joined to tRNAs, followed by tRNA and aminoacyl-tRNA synthetase differentiation. Fidelity mechanisms froze the code by inhibiting further innovation. View Full-Text
Keywords: aminoacyl-tRNA synthetase; Elongation Factor-Tu latch; evolution; genetic code; last universal common cellular ancestor; origin of life; polyglycine; tRNA aminoacyl-tRNA synthetase; Elongation Factor-Tu latch; evolution; genetic code; last universal common cellular ancestor; origin of life; polyglycine; tRNA
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Lei, L.; Burton, Z.F. Evolution of Life on Earth: tRNA, Aminoacyl-tRNA Synthetases and the Genetic Code. Life 2020, 10, 21.

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