Codon evolution and conservation of the reading phase in genetic code translation

Tohá, J.; Donoso, Rodrigo; Estay, Marlis; Diaz-Valdes, J.

doi:10.1016/0306-9877(89)90035-2

Cited by 1 publication

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“…Many authors have suggested that a simpler code preceded the modern code, but the reasoning and predicted codes have been varied and not closely related to what we will describe (31)(32)(33)(34)(35). In assigning amino acids to doublet codons, we have chosen the amino acid assigned to the majority of triplet codons in which the first two bases are common, with ties broken in favor of the simpler amino acid (upper lines of Fig.…”

Section: Mapping Of the Modern Genetic Code Onto A Simpler Doublet Codementioning

confidence: 99%

A mechanism for the association of amino acids with their codons and the origin of the genetic code

Copley

Smith

Morowitz

2005

Proc. Natl. Acad. Sci. U.S.A.

117

110

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The genetic code has certain regularities that have resisted mechanistic interpretation. These include strong correlations between the first base of codons and the precursor from which the encoded amino acid is synthesized and between the second base of codons and the hydrophobicity of the encoded amino acid. These regularities are even more striking in a projection of the modern code onto a simpler code consisting of doublet codons encoding a set of simple amino acids. These regularities can be explained if, before the emergence of macromolecules, simple amino acids were synthesized in covalent complexes of dinucleotides with ␣-keto acids originating from the reductive tricarboxylic acid cycle or reductive acetate pathway. The bases and phosphates of the dinucleotide are proposed to have enhanced the rates of synthetic reactions leading to amino acids in a small-molecule reaction network that preceded the RNA translation apparatus but created an association between amino acids and the first two bases of their codons that was retained when translation emerged later in evolution.catalysis ͉ origin of life T he genetic code has many regularities (1), of which only a subset have explanations in terms of tRNA function (2) or robustness against deleterious effects of mutation (3, 4) or errors in translation (3, 5). There is a strong correlation between the first bases of codons and the biosynthetic pathways of the amino acids they encode (1, 6). Codons beginning with C, A, and U encode amino acids synthesized from ␣-ketoglutarate (␣-KG), oxaloacetate (OAA), and pyruvate, respectively. ¶ These correlations are especially striking in light of the structural diversity of amino acids whose codons share a first base. For example, codons for Glu and Pro both begin with C, and those for Cys and Leu begin with U. Codons beginning with G encode amino acids that can be formed by direct reductive amination of a simple ␣-keto acid. These include glycine, alanine, aspartate, and glutamate, which can be formed by reductive amination of glyoxalate, pyruvate, OAA, and ␣-KG, respectively. There is also a long-recognized relationship between the hydrophobicity of the amino acid and the second base of its codon (1). Codons having U as the second base are associated with the most hydrophobic amino acids, and those having A as the second base are associated with the most hydrophilic amino acids.We suggest that both correlations can be explained if, before the emergence of macromolecules, simple amino acids were synthesized from ␣-keto acid precursors covalently attached to dinucleotides that catalyzed the reactions required to synthesize specific amino acids (see Fig. 1). This is a significant departure from previous theories attempting to explain the regularities in the genetic code (3). The ''stereochemical'' hypothesis suggests that binding interactions between amino acids and their codons or anticodons dictated the structure of the genetic code (7-10). The ''coevolution'' hypothesis (6) suggests that the original genetic code specifi...

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Section: Mapping Of the Modern Genetic Code Onto A Simpler Doublet Codementioning

confidence: 99%

A mechanism for the association of amino acids with their codons and the origin of the genetic code

Copley

Smith

Morowitz

2005

Proc. Natl. Acad. Sci. U.S.A.

117

110

View full text Add to dashboard Cite

show abstract

Codon evolution and conservation of the reading phase in genetic code translation

Cited by 1 publication

References 4 publications

A mechanism for the association of amino acids with their codons and the origin of the genetic code

A mechanism for the association of amino acids with their codons and the origin of the genetic code

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