Waligora EA, Ramsey DM, Pryor EE, Lu H, Hollis T, Sloan GP, Deora R, Wozniak DJ
AmrZ beta-sheet residues are essential for DNA binding and transcriptional control of Pseudomonas aeruginosa virulence genes.
J Bacteriol. 2010 Oct;192(20):5390-401
Authors: Waligora EA, Ramsey DM, Pryor EE, Lu H, Hollis T, Sloan GP, Deora R, Wozniak DJ
AmrZ is a putative ribbon-helix-helix (RHH) transcriptional regulator. RHH proteins utilize residues within the ?-sheet for DNA binding, while the ?-helices promote oligomerization. AmrZ is of interest due to its dual roles as a transcriptional activator and as a repressor, regulating genes encoding virulence factors associated with both chronic and acute Pseudomonas aeruginosa infection. In this study, cross-linking revealed that AmrZ forms oligomers in solution but that the amino terminus, containing an unordered region and a ?-sheet, were not required for oligomerization. The first 12 unordered residues (extended amino terminus) contributed minimally to DNA binding. Mutagenesis of the AmrZ ?-sheet demonstrated that residues 18, 20, and 22 were essential for DNA binding at both activation and repressor sites, suggesting that AmrZ utilizes a similar mechanism for binding to these sites. Mice infected with amrZ mutants exhibited reduced bacterial burden, morbidity, and mortality. Direct in vivo competition assays showed a 5-fold competitive advantage for the wild type over an isogenic amrZ mutant. Finally, the reduced infection phenotype of the amrZ-null strain was similar to that of a strain expressing a DNA-binding-deficient AmrZ variant, indicating that DNA binding and transcriptional regulation by AmrZ is responsible for the in vivo virulence defect. These recent infection data, along with previously identified AmrZ-regulated virulence factors, suggest the necessity of AmrZ transcriptional regulation for optimal virulence during acute infection.
PMID: 20709902 [PubMed - in process]