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Polymorphic toxin systems: comprehensive characterization of trafficking modes, processing, mechanisms, immunity and ecology using comparative genomics

Thursday, October 11, 2012 — Poster Session IV

2:00 p.m. – 4:00 p.m.

Natcher Conference Center, Building 45




  • D Zhang
  • R de Souza
  • V Anantharaman
  • LM Iyer
  • L Aravind


We have identified a new polymorphic toxin system in bacteria that is characterized by a remarkable diversity of C-terminal toxin domains generated by recombination. In this study we systematically investigated this system. We found that this system is distributed across all major bacterial lineages and is delivered by eight secretory systems, including type-II, type-V, VI, VII, and poorly-characterized PVC, PrsW-dependent and MuF phage-capsid-like systems. We found that toxin trafficking is accompanied by autoproteolytic processing catalyzed by HINT, ZU5, PrsW, caspase-like, papain-like, and a novel metallopeptidase associated with the PVC system. We identified over 150 distinct toxin domains, including peptidases, nucleases, deaminases, ADP-ribosyltransferases, ADP ribosyl cyclases, glycosyltranferases and lipid and carbohydrate modifying enzymes. Over 90 immunity families were further found to counteract toxin domains. Phyletic pattern and life-style analysis indicate that polymorphic toxins and polyimmunity loci participate in cooperative behavior and facultative “cheating” in several ecosystems such as human oral cavity and soil. Multiple domains from these systems are repeatedly transferred to eukaryotes and their viruses. This provides insights regarding the emergence of key regulatory systems, such as ADP ribosylation, interaction of myosin VI with cargo proteins, mediation of apoptosis, hyphal heteroincompatibility, hedgehog signaling, arthropod toxins and different signaling messengers.

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