A comparative study of dynamic structures between phage 434 Cro and repressor proteins by normal mode analysis

Area of Science:

• Structural biology
• Computational biophysics
• Molecular dynamics

Background:

• Bacteriophage DNA-binding proteins like 434 Cro and 434 repressor share similar structures and regulate gene expression.
• These proteins utilize a helix-turn-helix (HTH) motif for site-specific DNA recognition.
• Understanding subtle structural and dynamic differences is crucial for explaining variations in their DNA-binding specificity.

Purpose of the Study:

• To compare the dynamic structures of 434 Cro and 434 repressor using normal mode analysis.
• To identify structural differences between the monomeric forms and DNA-bound complexes of these proteins.
• To correlate observed dynamic differences with known variations in their DNA-binding specificities.

Main Methods:

• Normal mode analysis (NMA) was applied to structural data of both 434 Cro and 434 repressor.
• Analyses were performed on both monomeric protein structures and their complexes with DNA.
• Correlative motions of residues within the HTH motif and their interactions were examined.

Main Results:

• Significant differences in correlated residue motions were identified between monomeric 434 Cro and 434 repressor, particularly involving residues within and facing the HTH motif.
• The first helix of the HTH motif shows distortion upon DNA complex formation for both proteins.
• 434 Cro's HTH motif residues exhibit stronger positive correlations in motion compared to 434 repressor, suggesting a link to specificity.

Conclusions:

• Dynamic structural comparison via NMA is a valuable tool for uncovering differences in highly similar proteins.
• Subtle differences in residue dynamics within the HTH motif correlate with the distinct DNA-binding specificities of 434 Cro and 434 repressor.
• This approach provides insights beyond traditional static structural comparisons.