Peptide backbone circularization enhances antifreeze protein thermostability.

Area of Science:

• Biochemistry
• Protein Engineering
• Cryobiology

Background:

• Antifreeze proteins (AFPs) prevent freezing damage in cold-adapted organisms by binding ice.
• AFPs have potential applications in biomedicine, agriculture, and industry, but are limited by thermal instability.
• Type III AFPs are small and thermolabile, making them a suitable model for stability studies.

Purpose of the Study:

• To enhance the thermostability of type III antifreeze proteins (AFPs).
• To explore protein backbone circularization as a method to improve AFP thermal resilience.
• To assess the impact of circularization on AFP ice-binding activity and structure.

Main Methods:

• Computational modeling and molecular dynamics simulations identified a suitable extein for circularization.
• Split intein-mediated ligation was used to create a circularized type III AFP.
• Ice-affinity purification isolated the circularized AFP from intein domains.
• Activity assays and NMR analysis evaluated the thermostability and ice-binding properties of the circularized AFP.

Main Results:

• Circularization via split intein ligation significantly enhanced AFP thermostability.
• The circularized AFP retained 40% of its activity after incubation at 100°C for 30 minutes.
• NMR analysis suggested enhanced thermostability or refolding capacity in the circularized protein compared to the wild-type.

Conclusions:

• Protein backbone circularization is an effective strategy to dramatically improve AFP thermostability.
• Enhanced thermostability broadens the potential industrial and commercial applications of AFPs.
• This approach offers a pathway to overcome limitations of AFPs in high-temperature processing and production.