Factors correlating with significant differences between X-ray structures of myoglobin.

Area of Science:

• Biophysics
• Structural Biology
• Protein Dynamics

Background:

• Understanding protein conformational differences is key for functional insights.
• Myoglobin exhibits variations across species (sperm whale, horse, pig) and ligand-bound states.

Purpose of the Study:

• To validate ideas about the origins of conformational differences in myoglobin.
• To investigate the role of crystal packing and ligand binding on myoglobin structure.

Main Methods:

• Principal Component Analysis (PCA) applied to 291 myoglobin structures.
• Distance difference matrices used for structural comparison.
• Analysis of intermolecular crystal lattice hydrogen bonds.

Main Results:

• Horse and pig myoglobin structures show compact clusters with minor variations.
• Sperm whale myoglobin structures exhibit more outliers, some resembling horse structures due to GH loop distortions.
• Crystal lattice interactions and unusual ligand binding correlate with observed conformational changes, particularly in whale myoglobin.

Conclusions:

• Crystal packing and unusual ligand binding can induce conformational changes in myoglobin.
• Some observed structural differences may be crystal artifacts rather than functionally relevant.
• The study highlights the importance of considering crystal environment when interpreting protein structures.