FIG 1.

OxyR2 regulation of ahpC. (A) Schematic representation of the genetic structure of oxyR1-prxA and oxyR2-ahpC regulons. (B) Sequence alignment of E. coli OxyR (OxyR_Ec), V. cholerae VC2636 (OxyR1_Vc), and V. cholerae VC0732 (OxyR2_Vc). Conserved cysteine residues are boxed. (C) ahpC expression. Wild type, ΔoxyR1 ΔoxyR2 mutants, or ΔoxyR1ΔoxyR2 mutants containing the P_ahpC-luxCDABE transcriptional fusion plasmids were grown standing in AKI medium at 37°C for 4 h followed by shaking for 1 h until mid-log phase was reached. H₂O₂ (50 μM final concentration) was added to indicated cultures, and cultures were shaken at 37°C for 2 h. Luminescence was then measured and reported normalized to OD₆₀₀. LU, luminescence unit. For complementation assays, 0.1% arabinose was included in the medium to activate pBAD-oxyR2. (D) The importance of cysteine residues in OxyR1 (left) and OxyR2 (right). pBAD-oxyR1^WT or pBAD-oxyR1^C199S was introduced into ΔoxyR1 (pP_prxA-luxCDABE), and pBAD-oxyR2^WT or pBAD-oxyR2^C206S was introduced into ΔoxyR2 (pP_ahpC-luxCDABE). Arabinose (0.1%) was used to induce the P_BAD promoter, and 50 μM H₂O₂ (final concentration) was added to activate OxyR1. Data shown represent the mean and standard deviation from three biological replicates. ns, not significant; *, Student t test P value of <0.05.