Preferential codon usage in prokaryotic genes: the optimal codon-anticodon interaction energy and the selective codon...

Area of Science:

• Molecular Biology
• Genetics
• Bioinformatics

Background:

• Synonymous codons offer alternative ways to encode amino acids.
• Codon usage bias is observed across different organisms and genes.
• Efficient gene expression relies on optimal translation rates.

Purpose of the Study:

• To investigate the rules governing synonymous codon selection in highly expressed genes.
• To test the hypothesis that codon usage optimizes codon-anticodon interaction energy for efficient translation.
• To explore the role of tRNA availability in codon selection.

Main Methods:

• Analysis of nucleotide sequences from highly expressed coding regions of bacteriophage MS2 and E. coli mRNAs.
• Comparison of codon usage in normal reading frames versus frameshift sequences.
• Evaluation of codon-anticodon interaction energies.

Main Results:

• Specific synonymous codons (NNU or NNC) are preferred in highly expressed genes.
• Codon selection favors intermediate codon-anticodon interaction strength over very strong or weak interactions.
• Codons recognized by minor tRNAs are avoided in highly expressed genes.
• These patterns are distinct in the normal reading frame compared to frameshift sequences.

Conclusions:

• Codon usage in highly expressed genes is a strategy to optimize translation efficiency.
• Both codon-anticodon interaction energy and adaptation to tRNA population are key evolutionary constraints.
• Weakly expressed genes exhibit opposite codon usage rules, suggesting distinct selective pressures.