First arrived, first served: competition between codons for codon-amino acid stereochemical interactions determined...

Area of Science:

• Biochemistry
• Origin of Life Studies
• Molecular Evolution

Background:

• The genetic code's codon-amino acid assignments may stem from stereochemical nucleotide-amino acid interactions.
• Wong's metabolic coevolution hypothesis posits early amino acids integrated into the genetic code first.

Purpose of the Study:

• To investigate if trinucleotide-amino acid affinities determined genetic code assignments based on the "first arrived, first served" principle.
• To analyze the role of surfaces versus solution in early proto-translation systems.

Main Methods:

• Empirical estimates of single nucleotide-amino acid affinities were used to approximate all 64 × 20 trinucleotide-amino acid affinities.
• Affinity analyses were conducted for both surface-bound and solution-phase interactions.

Main Results:

• Genetic code assignments on surfaces correlate with high affinities for early-integrated amino acids.
• Similar principles were observed for anticodon-amino acid assignments in solution.
• Trinucleotides competing for amino acids better explained affinities than the reverse.

Conclusions:

• Two independent proto-translation systems (surface and solution) likely converged to form the current translation system.
• Direct codon-amino acid interactions on surfaces and proto-tRNA interactions in solution coadapted.
• The findings suggest a prebiotic metabolism predated the self-organization of the genetic code.