Dominant Alcohol-Protein Interaction via Hydration-Enabled Enthalpy-Driven Binding Mechanism.

Area of Science:

• Biochemistry
• Physical Chemistry
• Molecular Biophysics

Background:

• Water's role in protein-ligand interactions is crucial, affecting binding thermodynamics.
• Focus has been on water network changes, but water-protein dynamics influence is less understood.
• Alcohols, as low-affinity drugs, present a model to study water's impact on binding.

Purpose of the Study:

• To investigate the influence of controlled protein hydration on alcohol-protein interactions.
• To determine the thermodynamic parameters (Gibbs free energy, enthalpy, entropy) of alcohol binding as a function of hydration.
• To elucidate the mechanism of alcohol binding and the role of water-protein interplay.

Main Methods:

• Alcohol adsorption isotherms were measured under varying protein hydration levels.
• In situ Nuclear Magnetic Resonance (NMR) detection was employed.
• Temperature dependence of isotherms was used to calculate binding thermodynamics.

Main Results:

• Two distinct types of alcohol binding were identified.
• Low-affinity, nonspecific binding is highly sensitive to hydration level and temperature.
• Binding shifts from entropy-driven to enthalpy-driven with increasing hydration (h ≈ 0.2), with water at charged/polar groups being critical.
• Enthalpy-entropy compensation drives a significant negative Gibbs free energy change at higher hydration.

Conclusions:

• Water-protein interplay is essential for understanding alcohol binding to proteins.
• Hydration level critically modulates the thermodynamics and mechanism of alcohol binding.
• This study provides insights into weak drug-protein interactions and the role of hydration.