FIG. 1.

Characterization of ExsA domains. (A) Regions corresponding to the NTD and CTD constructs used in this work are indicated with solid lines. The HTH motifs of ExsA as well as the predicted linker region (hatched box) are indicated. Amino acids are numbered with respect to the initiating methionine. (B) Steady-state expression levels of ExsA_His, NTD_His, and CTD_His in P. aeruginosa. A vector control (pJN105) (lane 1) (V) or arabinose-inducible plasmids expressing either full-length ExsA_His (lane 2), NTD_His (lane 3), or CTD_His (lane 4) were introduced into an exsA mutant. Cells were grown in T3SS-inducing medium in the presence of arabinose (0.5%), and cell lysate samples were subjected to immunoblot analyses using an anti-histidine monoclonal antibody. The expressed products are indicated with arrows, and cross-reactive bands that serve as loading controls are indicated with asterisks. (C) Transcriptional activation by ExsA, NTD, and CTD. A vector control or plasmids expressing full-length ExsA, NTD, or CTD were introduced into an exsA mutant carrying the P_exsC-lacZ, P_exsD-lacZ, or P_exoT-lacZ transcriptional reporters. Strains were grown under inducing conditions for T3SS gene expression in the presence of arabinose (0.5%) and assayed for β-galactosidase activity. Note that the y axis is plotted on a logarithmic scale. Reported values (Miller units) are the averages from three independent experiments, and error bars indicate the standard errors of the means.