Protein conformational entropy is not slaved to water

Area of Science:

• Biophysics
• Structural Biology
• Protein Dynamics

Background:

• Conformational entropy plays a key role in protein functions like ligand binding.
• The
• solvent slaving
• model suggests protein motion is coupled to water dynamics.
• This model predicts protein-water interactions influence conformational entropy.

Purpose of the Study:

• To investigate the relationship between protein conformational entropy and solvent water interactions.
• To determine if changes in hydration affect fast internal protein dynamics.
• To challenge the predictions of the
• solvent slaving
• model regarding protein-water coupling.

Main Methods:

• Utilized Nuclear Magnetic Resonance (NMR) relaxation to detect fast internal side chain motion in proteins.
• Manipulated the hydration layer and bulk water conditions surrounding protein samples.
• Measured changes in protein dynamics under varied solvent conditions.

Main Results:

• Fast internal side chain dynamics of several proteins were unaffected by changes to hydration and bulk water.
• Protein motion and conformational entropy are not significantly dictated by solvent water interactions within the tested range.
• NMR relaxation data did not support the strong coupling predicted by the
• solvent slaving
• model.

Conclusions:

• Protein conformational entropy's role in function is independent of direct protein-water interactions.
• The
• solvent slaving
• model's predictions regarding protein-water coupling are not universally applicable.
• Fast internal protein dynamics are robust to changes in the aqueous environment.