Why is codon optimization used in expressing human proteins in bacteria?

Why is codon optimization used in expressing human proteins in bacteria?

• A. To change the amino acid sequence.
• B. To alter promoter strength.
• C. To match the host's codon usage and improve translation efficiency.
• D. To increase plasmid copy number.

Answer: (C)

The idea is to match the gene’s codons to what the host organism’s translation system handles best. Different organisms prefer different synonymous codons for the same amino acid because they have different sets of abundant tRNAs. When a human gene is put into a bacterium, the bacterium may encounter many codons that are rare for it, slowing down or stalling translation and lowering protein yield. Codon optimization changes those rare codons to synonymous ones that the bacterial tRNAs recognize more readily, speeding up elongation and improving overall translation efficiency. This keeps the amino acid sequence unchanged, since the substitutions code for the same residues, but it makes production in bacteria much more efficient. It isn’t about tweaking promoter strength or plasmid copy number, which affect transcription or DNA abundance, not the translation machinery.

The idea is to match the gene’s codons to what the host organism’s translation system handles best. Different organisms prefer different synonymous codons for the same amino acid because they have different sets of abundant tRNAs. When a human gene is put into a bacterium, the bacterium may encounter many codons that are rare for it, slowing down or stalling translation and lowering protein yield. Codon optimization changes those rare codons to synonymous ones that the bacterial tRNAs recognize more readily, speeding up elongation and improving overall translation efficiency. This keeps the amino acid sequence unchanged, since the substitutions code for the same residues, but it makes production in bacteria much more efficient. It isn’t about tweaking promoter strength or plasmid copy number, which affect transcription or DNA abundance, not the translation machinery.