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A Visual Assay to Monitor T6SS-mediated Bacterial Competition
Published on: March 20, 2013
Structural basis for type VI secretion effector recognition by a cognate immunity protein.
Mo Li1, Isolde Le Trong, Mike A Carl
1Department of Microbiology, University of Washington, Seattle, Washington, United States of America.
Plos Pathogens
|April 19, 2012
Summary
The type VI secretion system (T6SS) effector Tse2 induces cell quiescence, not death. Its immunity protein, Tsi2, protects Pseudomonas aeruginosa by interacting with an acidic patch, independent of dimer stability.
Area of Science:
- Microbiology
- Molecular Biology
- Structural Biology
Background:
- The type VI secretion system (T6SS) is crucial for interbacterial interactions, with Pseudomonas aeruginosa employing it to deliver effector proteins like Tse2.
- Tse2 inhibits target cell proliferation, conferring a fitness advantage to P. aeruginosa, while the immunity protein Tsi2 neutralizes its toxic effects.
Purpose of the Study:
- To elucidate the mechanism by which Tse2 induces cell quiescence rather than death in recipient cells.
- To investigate the molecular basis of Tsi2-mediated immunity against the Tse2 effector.
- To characterize the structural and functional relationship of the Tse2-Tsi2 effector-immunity pair.
Main Methods:
- Determined the 1.00 Å X-ray crystal structure of the Tsi2 immunity protein.
- Conducted a genetic screen to identify Tsi2 mutants defective in Tse2 interaction.
- Analyzed the interaction between Tsi2 and Tse2, and the role of Tsi2 dimer stability.
Main Results:
- Tse2 delivered via T6SS induces cell quiescence, not lysis, in target cells.
- The Tsi2 immunity protein protects against Tse2, with Tsi2's acidic patch mediating toxin interaction.
- Tsi2 dimer stability is not essential for Tse2 interaction or immunity, distinguishing it from other systems.
Conclusions:
- The Tse2-Tsi2 system exhibits unique features compared to known toxin-immunity and toxin-antitoxin systems.
- Structural insights into Tsi2 reveal its dimeric assembly and the functional importance of an acidic patch for immunity.
- This study advances understanding of T6SS effector secretion mechanisms and bacterial competition strategies.
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