High-energy channeling in protein folding

Area of Science:

• Biochemistry
• Protein Folding Dynamics
• Chemical Physics

Background:

• Characterizing high-energy states in protein folding is experimentally challenging due to their transient nature.
• Understanding these states is crucial for resolving controversies surrounding populated intermediates in protein folding pathways.

Purpose of the Study:

• To explore the energetics of high-energy states in protein folding.
• To map the free-energy profile for the folding of the two-state protein U1A.
• To elucidate the folding mechanism of U1A, focusing on transition state properties.

Main Methods:

• Analysis of nonlinearities in the Guanidinium hydrochloride (GdnHCl) dependence of activation energy for unfolding.
• Interpretation of these nonlinearities in terms of structural changes in the protein-folding transition state.

Main Results:

• The protein U1A folds via a high-energy channeling mechanism.
• The majority of conformational search occurs isoenergetically at the transition-state level.
• A broad and flat activation barrier was observed, covering over 60% of the reaction coordinate.

Conclusions:

• The folding pathway of U1A is determined by the sequence's capacity to stabilize productive transition states.
• The findings support a model where folding is guided by stabilizing interactions within a wide transition-state ensemble.