Enhancing protein stability with extended disulfide bonds.

Area of Science:

• Protein engineering
• Biochemistry
• Molecular biology

Background:

• Disulfide bonds are crucial for protein folding and stability.
• Cysteine-mediated disulfide bonds have inherent distance and angle limitations.
• Conventional mutagenesis has limitations in expanding protein functionality.

Purpose of the Study:

• To genetically encode noncanonical amino acids with long side-chain thiols.
• To create extended disulfide bonds for cross-linking distant protein sites.
• To improve protein stability and functionality beyond canonical limitations.

Main Methods:

• Genetic encoding of noncanonical amino acids in bacterial and mammalian systems.
• Incorporation of amino acids with long side-chain thiols into proteins.
• Growth-based selection experiments using mutant libraries at nonpermissive temperatures.
• Characterization of mutant enzymes with novel disulfide bonds.

Main Results:

• Successful incorporation of noncanonical amino acids into proteins with high fidelity.
• Formation of extended disulfide bonds capable of cross-linking distant sites.
• Identification of a mutant β-lactamase stabilized by an extended disulfide bond, showing a ~9 °C increase in stability.
• Demonstration of improved protein properties through unique cross-linking mechanisms.

Conclusions:

• Expanded amino acid building blocks enable novel protein engineering strategies.
• Extended disulfide bonds offer a unique mechanism for enhancing protein stability and function.
• This approach expands the toolkit for creating proteins with improved properties beyond conventional methods.