Adaptation of DNA to Protein Binding Revealed by Spectroscopy and Molecular Simulation

Area of Science:

• Structural biology
• Molecular biology
• Biophysics

Background:

• DNA exhibits conformational diversity (e.g., B-DNA, A-DNA), crucial for cellular processes like gene regulation.
• Histone-like nucleoid structuring protein (H-NS) in bacteria interacts with DNA, but the molecular basis for its AT-rich DNA preference is unclear.
• Understanding sequence-dependent DNA-protein interactions is key to deciphering regulatory mechanisms.

Purpose of the Study:

• To elucidate the molecular and structural basis for H-NS recognition of AT-rich DNA sequences.
• To investigate how H-NS binding influences DNA conformation and flexibility.
• To explore the broader implications of DNA structural adaptability in protein-DNA interactions.

Main Methods:

• Combined fluorescence spectroscopy, circular dichroism (CD), and molecular dynamics (MD) simulations.
• Utilized enhanced sampling techniques to analyze H-NS-DNA interactions.
• Quantified binding affinities for different DNA sequences (ApT vs. GpC repeats).

Main Results:

• H-NS demonstrated a 10-fold higher affinity for ApT repeats compared to GpC repeats.
• H-NS binding induced significant DNA structural changes: increased bending flexibility, minor groove widening, and A-like DNA features.
• GC-rich DNA remained conformationally closer to the canonical B-form upon H-NS interaction.

Conclusions:

• H-NS exploits the intrinsic conformational plasticity of DNA for sequence-specific binding.
• DNA structural adaptation is a key mechanism utilized by DNA-binding proteins for regulatory control.
• This study provides insights into how DNA's inherent properties shape protein-DNA interactions in biological systems.