THz time scale structural rearrangements and binding modes in lysozyme-ligand interactions

Area of Science:

• Biophysics
• Structural Biology
• Enzymology

Background:

• Understanding protein conformational changes is crucial for elucidating protein function, especially during substrate binding.
• Protein-ligand interactions induce motions governed by global protein modes, yet the internal fluctuations enabling these changes remain poorly characterized.

Purpose of the Study:

• To investigate the picosecond timescale binding modes and collective structural rearrangements in hen egg white lysozyme (HEWL) upon binding with the inhibitor (NAG)3 using Terahertz (THz) spectroscopy.
• To characterize the fast, collective motions that facilitate protein-ligand binding and substrate recognition.

Main Methods:

• Terahertz (THz) spectroscopy was employed to study the dynamic behavior of hen egg white lysozyme (HEWL) in its unbound and inhibitor-bound states.
• Analysis focused on picosecond timescale collective motions and structural rearrangements, including hydrogen-bonding dynamics in the hydration shell and modifications within the hydrophobic core.

Main Results:

• Upon inhibitor binding, HEWL's global backbone motion shifts from a dominant large-scale mode to a twisting deformation that facilitates binding cleft closure.
• Picosecond timescale hydrogen-bonding rearrangements in the hydration shell alter local hydrophobic core packing density.
• These localized intramolecular variations promote cooperative movements in the interfacial region, mediating binding.

Conclusions:

• The study reveals that THz-detected picosecond timescale fluctuations in the HEWL-(NAG)3 system are key to large-scale conformational changes.
• These dynamics, including hydrogen-bonding rearrangements and hydrophobic core modifications, facilitate substrate recognition and binding.
• Investigating fast, collective protein dynamics offers insights into the mechanisms of enzyme function and substrate binding.