How quickly can a β-hairpin fold from its transition state?

Area of Science:

• Biochemistry
• Structural Biology
• Chemical Physics

Background:

• Understanding protein folding mechanisms is crucial for elucidating biological processes.
• Identifying transition states is key to understanding folding dynamics.
• Current methods like Φ-value analysis infer transition state structures.

Purpose of the Study:

• To investigate if protein cross-linking can stabilize folding transition states.
• To explore cross-linking as a method to mimic and study protein folding transition states.
• To assess the impact of cross-linking on protein folding rates and barriers.

Main Methods:

• Introducing disulfide cross-linkers into a model β-hairpin (Trpzip4).
• Measuring folding rates of cross-linked and uncross-linked peptides.
• Analyzing the free energy landscape of cross-linked peptides.
• Empirical analysis of folding time dependence on hydrogen bond formation.

Main Results:

• Cross-linking β-strands near the turn significantly increased folding rate.
• Cross-linking termini resulted in a hyperstable hairpin with unchanged folding rate.
• Cross-linking can stabilize transition state analogues for direct folding assessment.
• Folding time follows a power law dependence on hydrogen bonds when barriers are absent.

Conclusions:

• Protein cross-linking is a viable strategy to manipulate folding free energy barriers.
• Cross-linking can stabilize folding transition state analogues, enabling direct folding process assessment.
• Folding dynamics of β-hairpins without significant free energy barriers can be described by a power law relationship.