Structural and functional characterization of VapBC52 toxin-antitoxin system from Mycobacterium tuberculosis

Area of Science:

• Microbiology
• Structural Biology
• Molecular Biology

Background:

• Mycobacterium tuberculosis possesses numerous uncharacterized toxin-antitoxin (TA) systems.
• TA systems are critical for bacterial survival, virulence, and stress response.

Purpose of the Study:

• To elucidate the structural and functional characteristics of the VapBC52 TA system from Mycobacterium tuberculosis.
• To investigate the role of VapBC52 in Mtb pathogenesis and potential antiphage defense.

Main Methods:

• X-ray crystallography was used to determine the structures of VapC52 toxin and the VapBC52 complex.
• In vitro assays were performed to assess tRNA cleavage activity and VapB52 auto-cleavage.
• Growth inhibition assays in Mycobacterium smegmatis and intracellular growth studies in macrophages and guinea pigs were conducted.

Main Results:

• The crystal structures revealed a unique dimeric conformation for VapC52 and a distinct architecture for VapB52, binding VapC52 at a 1:2 stoichiometry.
• VapC52 cleaves tRNA, inhibiting mycobacterial growth, while ssDNA binding activates VapB52, leading to its auto-cleavage.
• The vapBC52 locus is essential for intracellular Mtb growth and confers resistance to phage infection.

Conclusions:

• VapBC52 exhibits a unique structural basis for its function and plays a significant role in Mtb pathogenesis.
• The VapBC52 system is involved in intracellular survival and potentially in antiphage defense mechanisms in M. tuberculosis.