tRNA^fMet Inactivating Mycobacterium tuberculosis VapBC Toxin-Antitoxin Systems as Therapeutic Targets

Area of Science:

• Microbiology
• Molecular Biology
• Drug Discovery

Background:

• Toxin-antitoxin (TA) systems are abundant in Mycobacterium tuberculosis, with 50 belonging to the VapBC family.
• VapC toxin activity is regulated by VapB antitoxin binding, with free toxin being active and bound toxin being inactive.

Purpose of the Study:

• To identify the cellular targets of M. tuberculosis VapC2 and VapC21 toxins.
• To explore the potential of VapBC systems for antitubercular drug development.

Main Methods:

• Utilized a specialized 5' RNA sequencing (RNA-seq) approach to determine the in vivo RNA targets of VapC2 and VapC21.
• Performed site-directed mutagenesis on conserved amino acids in the VapB antitoxin to assess their role in toxin-antitoxin interaction.

Main Results:

• Both VapC2 and VapC21 toxins were found to exclusively cleave initiator tRNAfMet at the anticodon loop, inhibiting translation.
• Expression of VapC toxins led to potent translation inhibition, growth arrest, and cell death.
• Mutations in the VapB antitoxin significantly reduced its ability to neutralize VapC toxin activity.

Conclusions:

• The VapBC2 and VapBC21 systems provide a novel framework for developing specific bactericidal antitubercular agents.
• Targeting the VapB-VapC interaction site could lead to constitutive inactivation of tRNAfMet, offering a new therapeutic strategy.