Solvent effects on myoglobin conformational substates as studied by electron paramagnetic resonance

Area of Science:

• Biophysics
• Structural Biology
• Spectroscopy

Background:

• Horse myoglobin is a key protein for studying oxygen transport.
• Understanding protein dynamics is crucial for biological function.
• Electronic paramagnetic resonance (EPR) spectroscopy is sensitive to local protein environments.

Purpose of the Study:

• To investigate the influence of pH and organic solvents on horse myoglobin's conformational substates.
• To analyze the distribution of ferric ion crystal field parameters using EPR.
• To correlate spectral changes with protein dynamics.

Main Methods:

• Analysis of frozen horse myoglobin solutions using electronic paramagnetic resonance (EPR) spectroscopy.
• Computer simulations of EPR spectra employing Gaussian distributions of ferric ion crystal field parameters.
• Varying solution pH and incorporating different organic solvents, including glycerol.

Main Results:

• EPR spectral analysis revealed that both pH and organic solvents affect the mean values and variances of ferric ion crystal field parameter distributions.
• A significant narrowing of the conformational substate distribution was observed upon addition of glycerol.
• These findings suggest that solvent composition and pH modulate protein flexibility.

Conclusions:

• The conformational substates of horse myoglobin are sensitive to environmental factors like pH and solvent composition.
• Glycerol, in particular, reduces the heterogeneity of protein conformations.
• EPR spectroscopy combined with computer simulation provides a powerful tool for probing protein dynamics and conformational heterogeneity.