Simple physical models connect theory and experiment in protein folding kinetics

Area of Science:

• Biophysics
• Computational Biology
• Protein Science

Background:

• The protein-folding problem remains a central challenge in molecular biology.
• Understanding folding principles requires robust theoretical models validated by experimental data.

Purpose of the Study:

• To extend existing protein folding models by incorporating hydrogen bonding and backbone torsion strain.
• To evaluate the predictive power of the refined model for protein folding kinetics and phi-values.
• To gain insights into alternative folding pathways and the validity of quasi-equilibrium assumptions.

Main Methods:

• Developed an extended model of folding free energy landscapes.
• Integrated factors for hydrogen bonding and backbone torsion strain.
• Employed a hybrid approach combining master equations and transition state theory for kinetic analysis.
• Compared model predictions of folding phi-values and transition state free energy barriers with experimental data for multiple proteins.

Main Results:

• Achieved strong correlations (r=0.41–0.88) between calculated and experimental folding phi-values for over half of 19 tested proteins.
• Demonstrated a significant correlation (r=0.69) between calculated transition state free energy barriers and measured folding rates for 37 proteins.
• Provided insights into the role of alternative pathways and the accuracy of quasi-equilibrium approximations in protein folding.

Conclusions:

• The refined model effectively captures key aspects of protein folding, including kinetics and intermediate states.
• The study validates the use of native-state-based models while acknowledging their limitations.
• Predictions for over 400 protein domains offer a broader test of the model's generalizability and potential for future research.