Programmed secretion arrest and receptor-triggered toxin export during antibacterial contact-dependent growth inhibition

• Zachary c. Ruhe ^[1] ; Poorna Subramanian ^[2] ; Kiho Song ^[1]
  1. [1] University of California, Santa Barbara

     University of California, Santa Barbara

     Estados Unidos

     
  2. [2] California Institute of Technology

     California Institute of Technology

     Estados Unidos

     
• Localización: Cell, ISSN 0092-8674, Vol. 175, Nº. 4, 2018, págs. 921-933
• Idioma: inglés
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• Resumen

  • Contact-dependent growth inhibition (CDI) entails receptor-mediated delivery of CdiA-derived toxins into Gram-negative target bacteria. Using electron cryotomography, we show that each CdiA effector protein forms a filament extending ∼33 nm from the cell surface. Remarkably, the extracellular filament represents only the N-terminal half of the effector. A programmed secretion arrest sequesters the C-terminal half of CdiA, including the toxin domain, in the periplasm prior to target-cell recognition. Upon binding receptor, CdiA secretion resumes, and the periplasmic FHA-2 domain is transferred to the target-cell outer membrane. The C-terminal toxin region of CdiA then penetrates into the target-cell periplasm, where it is cleaved for subsequent translocation into the cytoplasm. Our findings suggest that the FHA-2 domain assembles into a transmembrane conduit for toxin transport into the periplasm of target bacteria. We propose that receptor-triggered secretion ensures that FHA-2 export is closely coordinated with integration into the target-cell outer membrane.