FIGURE 1.

C58 is indispensable for TcpP activation of virulence gene expression. (A) V. cholerae ΔtcpP strains containing P_BAD-controlled plasmids harboring TcpP or its cysteine mutant derivatives and a P_toxT-lux transcriptional fusion plasmid were grown in LB with 0.01% arabinose in the presence or absence of taurocholate acid at 37°C until OD600 ≈ 0.2. Luminescence was measured and reported as light units/OD₆₀₀. Data are the means ± SD (n = 3). (B) V. choleraeΔtcpP strains containing P_BAD-TcpP wild type or cysteine mutant plasmids grown in LB with 0.01% arabinose in the presence of 1 mM TC for 6 h. Cell lysates (0.1 mg) were applied to SDS-PAGE, and subjected to Western blotting using an anti-TcpP or anti-TcpA antibody.