ExsA Activates Type III Secretion System Gene Expression in Pseudomonas aeruginosa

Strategic Insights -

Research has shown that ExsA, a member of the AraC family of transcriptional regulators, plays a critical role in activating the type III secretion system (T3SS) in Pseudomonas aeruginosa. This process involves the binding of ExsA to specific DNA sequences, a mechanism that is conserved across different bacterial species. However, the distinct oligomeric states of ExsA and its homologues, LcrF/VirF, influence their interactions with promoter DNA. Additionally, mutations that disrupt the ExsA consensus binding site in both Pseudomonas aeruginosa and Yersinia pestis T3SS promoters prevent activation by ExsA and LcrF.

Key Takeaways:

  • ExsA, a member of the AraC family of transcriptional regulators, activates T3SS gene expression in Pseudomonas aeruginosa.
  • ExsA recognizes a common nucleotide sequence with LcrF/VirF, suggesting a conserved mechanism of T3SS regulation.
  • The distinct oligomeric states of ExsA and LcrF/VirF influence their interactions with promoter DNA.
  • Mutations that disrupt the ExsA consensus binding site in Pseudomonas aeruginosa and Yersinia pestis T3SS promoters prevent activation by ExsA and LcrF.
  • ExsA and LcrF/VirF are sensitive to mutations that disrupt the ExsA consensus binding site, indicating a shared mechanism of T3SS regulation.
  • The research also demonstrated that the activators of T3SS gene expression from Photorhabdus luminescens, Aeromonas hydrophila, and Vibrio parahaemolyticus are sensitive to mutations that disrupt the ExsA consensus binding site.

Research was conducted by J.M. King and colleagues, published in the Journal of Bacteriology in 2013.

Statistics:

  • The study demonstrated that ExsA and LcrF/VirF recognize a common nucleotide sequence.
  • Two ExsA monomers are sequentially recruited to the promoter region.
  • LcrF binds to promoter DNA as a preformed dimer.
  • The binding capacity of LcrF to promoter DNA is higher than ExsA.
  • The research showed that LcrF mutant defective for dimerization binds promoter DNA with properties similar to ExsA.

Sources:

  • ExsA and LcrF Recognize Similar Consensus Binding Sites, but Differences in Their Oligomeric State Influence Interactions with Promoter DNA. Journal of Bacteriology, 2013;195(24):5639-5650.
  • American Society for Microbiology - www.asm.org
  • Journal of Bacteriology - jb.asm.org