Induced DNA bending by unique dimerization of HigA antitoxin

Area of Science:

• Molecular Biology
• Structural Biology
• Microbiology

Background:

• Bacterial toxin-antitoxin (TA) systems regulate cell growth during stress.
• Mycobacterium tuberculosis (TB pathogen) possesses three HigBA type II TA systems.
• Type II TA modules are typically autoregulated by the antitoxin protein.

Purpose of the Study:

• To determine the crystal structure of the M. tuberculosis HigA3 antitoxin (MtHigA3).
• To elucidate the interaction between MtHigA3 and its operator DNA.
• To understand the structural basis of HigBA system regulation in M. tuberculosis.

Main Methods:

• X-ray crystallography was used to determine the structure of MtHigA3 and its DNA complex.
• Nuclear Magnetic Resonance (NMR) spectroscopy investigated MtHigA3-DNA interactions.
• Comparative structural analysis of HigA homologues.

Main Results:

• The MtHigA3 antitoxin forms a homodimer with a DNA-binding domain (N-terminus) and dimerization domain (C-terminus).
• MtHigA3 binds promoter DNA via two helix-turn-helix (HTH) motifs, inducing a 46.5° bend.
• A unique β-lid in MtHigA3 facilitates tight dimerization and influences DNA curvature interaction.

Conclusions:

• The study provides atomic-level insights into the M. tuberculosis HigBA system.
• Structural features of MtHigA3, including the β-lid, are crucial for DNA binding and dimerization.
• Understanding this TA system could inform the development of novel antibiotics against tuberculosis.