Initial Amino Acid:Codon Assignments and Strength of Codon:Anticodon Binding.

Area of Science:

• Molecular Biology
• Origin of Life Studies
• Biochemistry

Background:

• Ribosomes facilitate peptide synthesis by binding aminoacyl-tRNAs and peptidyl-tRNAs.
• This binding involves anticodon:codon pairing on mRNA and acceptor stem interactions at the peptidyl transferase center.

Purpose of the Study:

• To investigate the role of intrinsic codon:anticodon binding strength in early ribosomal peptide synthesis.
• To determine if early amino acid assignments correlated with codon binding affinity.

Main Methods:

• Measured binding affinities between anticodon stem loops and short oligonucleotides representing codons.
• Compared binding strengths of family-box versus split-box codon pairings.

Main Results:

• Family-box codon:anticodon pairings exhibit significantly tighter binding than split-box pairings.
• Two family-box anticodon stem loops can simultaneously bind adjacent codons, unlike split-box pairings.
• Amino acids encoded by family boxes are consistent with those produced by early cyanosulfidic chemistry.

Conclusions:

• Intrinsic codon:anticodon binding strength likely influenced early amino acid assignments in peptide synthesis.
• Family-box codons, with their tighter binding, may represent the earliest set of codons used.
• This supports the hypothesis that early peptide synthesis utilized a limited set of amino acids accessible through primordial chemistries.