An Engineered Rare Codon Device for Optimization of Metabolic Pathways

Area of Science:

• Molecular Biology
• Synthetic Biology
• Metabolic Engineering

Background:

• Rare codons typically halt protein translation due to the scarcity of their corresponding transfer RNAs (tRNAs).
• This translational pausing can be harnessed as a regulatory mechanism for controlling gene expression levels.

Purpose of the Study:

• To engineer a molecular device for precise control of protein expression using rare codons.
• To demonstrate the device's ability to switch gene expression on/off and modulate it to intermediate levels.
• To apply the device for optimizing metabolic pathways in Escherichia coli.

Main Methods:

• Insertion of rare codons into reporter genes to establish a linear relationship between codon copy number and expression levels.
• Construction of a molecular device in E. coli utilizing the AGG rare codon, its cognate tRNA, a modified tRNA, and truncated aspartyl-tRNA synthetase (TDRS).
• Application of the rare codon device to modulate the expression of four genes in the fatty acid synthesis II (FASII) pathway.

Main Results:

• A linear correlation was established between gene expression levels and the copy number of inserted rare codons.
• The molecular device successfully switched reporter gene expression on/off and achieved tunable intermediate expression levels.
• Modulating FASII pathway gene expression resulted in nearly a two-fold increase in fatty acid yield.

Conclusions:

• Rare codons can be effectively utilized to construct a molecular device for precise gene expression regulation.
• The developed device offers a novel method for controlling protein synthesis levels and optimizing metabolic pathways.
• This approach has potential applications in biotechnology for enhancing the production of valuable compounds.