Coupled motion in proteins revealed by pressure perturbation

Area of Science:

• Biophysics
• Protein dynamics
• Structural biology

Background:

• Protein function relies on substructure and internal motion, but experimental data is limited.
• Understanding protein dynamics under varying conditions is crucial for comprehending stability and folding.
• Hydrostatic pressure is a powerful tool to probe molecular interactions and conformational states.

Purpose of the Study:

• To investigate the effects of high pressure on fast internal motions in ubiquitin using NMR relaxation.
• To characterize the pressure dependence of side chain and main chain motions in proteins.
• To explore the relationship between pressure response, compressibility, and protein conformational states.

Main Methods:

• Nuclear Magnetic Resonance (NMR) relaxation measurements were employed.
• High pressure was applied to study the effects on protein internal motion.
• Analysis focused on the pressure dependence of methyl-bearing side chain and main chain dynamics.

Main Results:

• Side chain motions exhibit significant and variable pressure dependence, unlike main chain motions.
• Pressure sensitivity of core side chains correlates with their motion at ambient pressure.
• Localized cooperativity of sub-nanosecond motions and variable compressibility were observed.

Conclusions:

• The native ensemble of ubiquitin likely contains members resembling the "dry molten globule" state.
• Variable side-chain conformational entropy contributes to the thermodynamic architecture of protein stability.
• These findings advance our understanding of protein folding, stability, and function.