Structure of Tsi2, a Tse2-immunity protein from Pseudomonas aeruginosa

Experimental Data Snapshot

  • Resolution: 1.00 Å
  • R-Value Free: 0.176 
  • R-Value Work: 0.145 
  • R-Value Observed: 0.147 

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Structural Basis for Type VI Secretion Effector Recognition by a Cognate Immunity Protein.

Li, M.Le Trong, I.Carl, M.A.Larson, E.T.Chou, S.De Leon, J.A.Dove, S.L.Stenkamp, R.E.Mougous, J.D.

(2012) PLoS Pathog 8: e1002613-e1002613

  • DOI: https://doi.org/10.1371/journal.ppat.1002613
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 

    The type VI secretion system (T6SS) has emerged as an important mediator of interbacterial interactions. A T6SS from Pseudomonas aeruginosa targets at least three effector proteins, type VI secretion exported 1-3 (Tse1-3), to recipient Gram-negative cells. The Tse2 protein is a cytoplasmic effector that acts as a potent inhibitor of target cell proliferation, thus providing a pronounced fitness advantage for P. aeruginosa donor cells. P. aeruginosa utilizes a dedicated immunity protein, type VI secretion immunity 2 (Tsi2), to protect against endogenous and intercellularly-transferred Tse2. Here we show that Tse2 delivered by the T6SS efficiently induces quiescence, not death, within recipient cells. We demonstrate that despite direct interaction of Tsi2 and Tse2 in the cytoplasm, Tsi2 is dispensable for targeting the toxin to the secretory apparatus. To gain insights into the molecular basis of Tse2 immunity, we solved the 1.00 Å X-ray crystal structure of Tsi2. The structure shows that Tsi2 assembles as a dimer that does not resemble previously characterized immunity or antitoxin proteins. A genetic screen for Tsi2 mutants deficient in Tse2 interaction revealed an acidic patch distal to the Tsi2 homodimer interface that mediates toxin interaction and immunity. Consistent with this finding, we observed that destabilization of the Tsi2 dimer does not impact Tse2 interaction. The molecular insights into Tsi2 structure and function garnered from this study shed light on the mechanisms of T6 effector secretion, and indicate that the Tse2-Tsi2 effector-immunity pair has features distinguishing it from previously characterized toxin-immunity and toxin-antitoxin systems.

  • Organizational Affiliation

    Department of Microbiology, University of Washington, Seattle, Washington, United States of America.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Type VI secretion immunity protein
A, B
85Pseudomonas aeruginosaMutation(s): 0 
Gene Names: PA2703
Find proteins for Q9I0D9 (Pseudomonas aeruginosa (strain ATCC 15692 / DSM 22644 / CIP 104116 / JCM 14847 / LMG 12228 / 1C / PRS 101 / PAO1))
Explore Q9I0D9 
Go to UniProtKB:  Q9I0D9
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ9I0D9
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 1.00 Å
  • R-Value Free: 0.176 
  • R-Value Work: 0.145 
  • R-Value Observed: 0.147 
  • Space Group: P 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 27.807α = 110.48
b = 34.063β = 95.94
c = 37.65γ = 95.82
Software Package:
Software NamePurpose
ADSCdata collection
HKL-2000data reduction
HKL-2000data scaling

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2012-03-21
    Type: Initial release
  • Version 1.1: 2012-05-02
    Changes: Database references
  • Version 1.2: 2024-02-28
    Changes: Data collection, Database references