Fast internal dynamics in alcohol dehydrogenase.

Area of Science:

• Biophysics
• Protein dynamics
• Neutron spectroscopy

Background:

• Large-scale domain motions in alcohol dehydrogenase (ADH) were previously observed using neutron spin-echo spectroscopy (NSE).
• Understanding protein dynamics is crucial for enzyme function and stability.

Purpose of the Study:

• To investigate the dynamics of alcohol dehydrogenase (ADH) in solution using high-resolution neutron spectroscopy.
• To identify and characterize internal motions beyond the slow domain movements.

Main Methods:

• Utilized high-resolution neutron time-of-flight (TOF) and neutron backscattering (BS) spectroscopy.
• Analyzed hydrogen dynamics in the incoherent scattering range.
• Interpreted data using three distinct mobility classes.

Main Results:

• Identified a fast internal dynamic process in ADH, in addition to slow global diffusion and domain motions.
• Approximately one-third of ADH protons participate in this fast, localized diffusive motion.
• The diffusion coefficient for these internal motions is about two-thirds that of the surrounding D2O solvent.

Conclusions:

• The fast internal process is likely associated with solvent-exposed amino acid residues, particularly those with dangling side chains.
• This study provides new insights into the complex dynamic behavior of ADH at a finer resolution.