- Escherichia coli Rosetta is a genetically engineered strain designed to enhance the expression of eukaryotic proteins in bacterial systems by addressing a common issue: codon bias.
- When expressing genes from higher organisms—such as humans or other mammals—in E. coli, translation can be inefficient due to the presence of rare codons that are infrequently used in bacterial genomes.
- The Rosetta strain solves this problem by supplying extra copies of tRNA genes for several rare codons, including those for arginine (AGG, AGA), isoleucine (AUA), leucine (CUA), proline (CCC), and glycine (GGA). These tRNAs are encoded on a chloramphenicol-resistant plasmid (typically pRARE), which must be maintained with appropriate antibiotic selection.
- Rosetta is often used as a derivative of BL21(DE3), making it compatible with the T7 promoter system for IPTG-inducible expression.
- It retains the protease-deficient background of BL21, improving the stability of recombinant proteins. Because the strain enhances the translation of mRNAs with non-optimized codon usage, it is especially useful for producing eukaryotic proteins, structural biology targets, or proteins with codon-rich regions that otherwise result in truncated or misfolded products in standard E. coli strains.
- There are also variants such as Rosetta(DE3) and Rosetta(DE3)pLysS, which include further features like tighter control of basal expression through T7 lysozyme. These are ideal when expressing proteins that are toxic to the host or require strict regulation.
- Overall, the Rosetta strain family significantly improves the success rate of expressing complex or difficult eukaryotic proteins in bacterial systems and is a valuable tool in structural genomics, proteomics, and therapeutic protein research.
