Enhancing Protein Stability with Genetically Encoded Noncanonical Amino Acids

Area of Science:

• Biochemistry
• Protein Engineering
• Synthetic Biology

Background:

• Expanding the genetic code with noncanonical amino acids allows for protein evolution with novel properties.
• Evolving proteins with enhanced thermal stability is crucial for various biotechnological applications.

Purpose of the Study:

• To investigate the impact of incorporating noncanonical amino acids on protein thermal stability.
• To engineer enhanced thermal properties in E. coli homoserine O-succinyltransferase (metA) using an expanded genetic code.

Main Methods:

• Creation of a mutant library of E. coli metA with randomly incorporated noncanonical amino acids.
• Selection of mutants exhibiting enhanced thermal properties.
• Characterization of a specific mutation substituting Phenylalanine 21 with (p-benzoylphenyl)alanine (pBzF).

Main Results:

• Substitution of Phe 21 with pBzF resulted in a 21 °C increase in the melting temperature of E. coli metA.
• This significant increase in thermal stability was attributed to a single mutation.
• A likely mechanism involves a covalent adduct between Cys 90 and the pBzF keto group, stabilizing the enzyme's dimeric form.

Conclusions:

• An expanded genetic code offers unique strategies for protein evolution.
• Single noncanonical amino acid substitutions can dramatically enhance protein thermal stability.
• This approach provides a powerful tool for engineering proteins with improved functional properties.