Figure 7. TetR induction by endogenous levels of a Trx1-TIP2 fusion in the promoter variants P_cat, P_cat -10CATTTA and P_cat -10CAGCCA.

(A) GFP fluorescence measurement to examine TetR induction by a chromosomally encoded Trx1-TIP2 fusion protein. The three promoter variants and the control strains − Salmonella WT, the reporter strain lacking TetR (P_tetA gfp+) and the promoter variants without TIP2 in the genome − were incubated without and with 400 nM dox. The bars illustrate the fluorescence intensity which was normalized to a 1 ml culture with OD₅₉₅ = 0.5. The data are a representative set from at least three independent measurements and display the mean ± standard deviation. (B) Western blot for determining the steady-state levels of endogenous or TIP2-tagged Trx1 in the three promoter variants. The proteins were detected by polyclonal antibodies against either Trx1 (top) or TIP2 (bottom). With Salmonella WT serving as control, 10 µg crude lysate of each strain were loaded onto the gels. DnaK served as loading control and was detected with a monoclonal anti-DnaK antibody.