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“Molecular insights into the bactericidal toxin Tle1 of Pseudomonas aeruginosa: Interaction with VgrG, its adaptor, and its immunity protein”

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Lefebvre, Delphine, Soscia, Chantal, Schmitt, Laura, Goulet, Adeline, Ize, Bérengère, Bleves, Sophie·2026·Journal of Biological Chemistry
DOI 10.1016/j.jbc.2026.111416

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Abstract

The Type VI secretion system delivers a wide range of antibacterial effectors, including phospholipases of the Tle family. Here, we characterize Tle1 from Pseudomonas aeruginosa and demonstrate that it functions as a bactericidal toxin when associated to the membranes in the periplasm. Bacterial two-hybrid assays revealed specific protein-protein interactions within the tle1 locus, involving the immunity protein Tli1a, the chaperone/adapter Tla1, and the spike protein VgrG4a. These interactions were independently validated by co-purification assays. Structural modeling with AlphaFold 3 produced a high-confidence ternary complex in which a VgrG4a trimer accommodates one Tle1 monomer and one Tla1 monomer. The three predicted interfaces (Tle1-Tla1, Tla1-VgrG4a, and Tle1-VgrG4a) were confirmed experimentally in vivo and important charged residues mediating these interfaces were identified. Furthermore, modeling of the Tle1-Tli1a complex suggests an inhibition mechanism that does not occlude the catalytic pocket. Consistently, Tli1a was localized to the outer membrane of P. aeruginosa, supporting in silico predictions of an outer membrane lipoprotein and positioning it ideally to neutralize periplasmic Tle1 activity. In contrast, we did not detect the second candidate immunity protein, Tli1b, either in P. aeruginosa or in Escherichia coli, and, following a bioinformatic analysis of the locus of the PAO1 strain, we propose that it is a pseudogene. Together, these findings elucidate the molecular interactions underlying Tle1 delivery and inhibition and highlight the role of Tli1a as a dedicated immunity protein that protects P. aeruginosa from self-intoxication.

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Metadata

Authors
Lefebvre, D., Soscia, C., Schmitt, L., Goulet, A., Ize, B., & Bleves, S.
Affiliations
Centre National de la Recherche Scientifique (FR)
Corresponding author
Bleves, Sophie
ORCID
Venue
Journal of Biological Chemistry
Publisher
Elsevier BV
Published
2026-05
Volume
302
Issue
5
Pages
111416
ISSN
0021-9258 (ISSN-L)
DOI
10.1016/j.jbc.2026.111416
OpenAlex
W7147646136
Cited by
0
References
2
FWCI
0.00
Type
journal article
Language
en
Open access
Licence
Locations
  • Journal of Biological Chemistry (publishedVersion, cc-by)
  • bioRxiv (Cold Spring Harbor Laboratory) (acceptedVersion)
  • PubMed (publishedVersion)
  • PubMed Central (publishedVersion, cc-by)
  • HAL (submittedVersion, other-oa)
  • HAL (submittedVersion)
Funders
  • Defeating Cystic Fibrosis Association (RF20240503476/1/1/69)
  • Foundation for Medical Research (FDT202404018453)
  • French National Research Agency (ANR-21-CE11-0028)
  • National Centre for Scientific Research
  • Aix-Marseille University
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Genetics › Bacterial Genetics and Biotechnology
  • Life Sciences › Immunology and Microbiology › Microbiology › Vibrio bacteria research studies
  • Life Sciences › Immunology and Microbiology › Microbiology › Escherichia coli research studies
Keywords
TLE1, Pseudomonas aeruginosa, type VI secretion system, immunity proteins, phospholipase, protein-protein interaction, ternary complex structure, outer membrane lipoprotein, pseudogenes, self-poisoning
MeSH terms
Bacterial Proteins, Bacterial Toxins, Models, Molecular, Pseudomonas aeruginosa

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