Adding L-3-(2-Naphthyl)alanine to the genetic code of E. coli

Area of Science:

• Biochemistry
• Molecular Biology
• Synthetic Biology

Background:

• The genetic code, comprising 20 standard amino acids, limits protein diversity and function.
• Site-specific incorporation of unnatural amino acids (UAAs) into proteins offers a route to expand this code.
• Previous methods for UAA incorporation faced challenges in efficiency and fidelity.

Purpose of the Study:

• To develop a robust method for site-specific incorporation of UAAs into proteins in Escherichia coli.
• To demonstrate the utility of an evolved orthogonal aminoacyl-tRNA synthetase (aaRS) system for UAA delivery.
• To assess the fidelity and applicability of this methodology for genetic code expansion.

Main Methods:

• Evolution of an orthogonal aminoacyl-tRNA synthetase (aaRS) specific for L-3-(2-naphthyl)alanine.
• Design and use of an orthogonal amber suppressor tRNA.
• Site-specific incorporation of L-3-(2-naphthyl)alanine into proteins in E. coli via amber nonsense codon suppression.
• Assessment of translational fidelity using the engineered system.

Main Results:

• Successfully incorporated the unnatural amino acid L-3-(2-naphthyl)alanine site-specifically into proteins in E. coli.
• Developed an orthogonal aaRS that selectively aminoacylates the UAA onto an orthogonal tRNA with high efficiency.
• Achieved translational fidelity greater than 99% for UAA incorporation in response to an amber nonsense codon.
• Demonstrated the potential applicability of this methodology to a wide range of UAAs.

Conclusions:

• The developed methodology enables efficient and high-fidelity site-specific incorporation of UAAs into proteins.
• This approach significantly expands the possibilities for protein engineering and functional studies.
• Expanding the genetic code with UAAs holds promise for enhancing protein and potentially organismal function.