The transcriptional regulator SsrB is involved in a molecular switch controlling virulence lifestyles of Salmonella
Fig 6
SsrB represses hilA by binding to the regulatory region between positions -100 to -35.
Expression of the hilA-cat-410+66 (A), hilA-cat-100+6 (B), hilA-cat-35+6 (C) and hilA-cat-35+446 (D) transcriptional fusions was tested in the WT S. Typhimurium strain with the vector pMPM-K3, or the plasmid pK3-SsrB, which expresses SsrB from a constitutive promoter. The CAT-specific activity was determined from bacterial cultures grown for 9 h in LB at 37°C. Data represents the mean with standard deviation of three independent experiments. *Statistically different values with respect to the WT strain with pMPM-K3, P < 0.005. EMSAs were performed to determine whether SsrB binds to the hilA DNA fragments in the hilA-cat-410+66 (E), hilA-cat-100+6 (F), hilA-cat-35+6 (G) and hilA-cat-35+446 (H) fusions. The DNA fragments were incubated with increasing concentrations of purified 6H-SsrBc (0, 0.5, 1, 1.5 and 2 μM). DNA-protein complexes are indicated by an asterisk.