Pressure, motion, and conformational entropy in molecular recognition by proteins

Area of Science:

• Biochemistry
• Structural Biology
• Biophysics

Background:

• Protein-ligand interactions are fundamental to biochemistry.
• Cryogenic structures have long informed binding thermodynamics.
• NMR-relaxation methods revealed conformational entropy's role in binding.

Purpose of the Study:

• Investigate pressure dependence of internal protein dynamics in barnase and its complex with barstar.
• Determine if protein dynamics are conserved along the pressure-binding thermodynamic cycle.
• Explore the role of conformational dynamics in adapting protein function to extreme environments.

Main Methods:

• Utilized NMR-relaxation methods to study fast internal motion.
• Analyzed pressure dependence of dynamics in barnase and barnase-barstar complex.
• Examined thermodynamic cycle under varying pressure conditions.

Main Results:

• Protein dynamics were conserved along the pressure-binding thermodynamic cycle.
• Barnase-barstar complex exhibits femtomolar affinity despite an entropic penalty at ambient pressure.
• At high pressure, binding occurred without a conformational entropy penalty due to conserved side-chain dynamics.
• Observed pressure and binding-induced clustering of dynamics, indicating conformational heterogeneity.

Conclusions:

• Protein dynamics are conserved under pressure, altering the thermodynamics of ligand binding.
• Conformational dynamics play a crucial role in protein function adaptation to extreme environments.
• Structural segregation of dynamics in barnase demonstrates the plasticity of conformational entropy contributions.