Figure 5. AlgQ interacts simultaneously with P. aeruginosa σ⁷⁰ regions 2 and 4.

A. Effect of amino acid substitution I392F in P. aeruginosa (Pa) σ⁷⁰ region 2 on its ability to interact with either Rsd or AlgQ. Results of β-galactosidase assays performed with FW102 O_L2–62 cells containing two compatible plasmids, one encoding λCI, a λCI-Rsd fusion protein, or a λCI-AlgQ fusion protein, and the other encoding the indicated α-Pa σ⁷⁰ region 2 fusion protein. The cells were grown in the presence of 10 μM IPTG. The graph shows the averages of three independent measurements and standard deviations.

B. Cartoon (top) depicts how unfused AlgQ can bridge a λCI-Pa σ⁷⁰ region 2 fusion protein and an α-Pa σ⁷⁰ region 4 fusion protein and thereby activate transcription from test promoter placO_L2-62. Results of β-galactosidase assays (graph) performed with FW102 O_L2–62 cells containing three compatible plasmids, one encoding the indicated λCI-Pa σ⁷⁰ region 2 fusion protein, a second encoding the indicated α-Pa σ⁷⁰ region 4 fusion protein, and a third encoding either unfused wild-type AlgQ or no AlgQ. The plasmids directed the synthesis of the fusion proteins (or AlgQ) under the control of IPTG-inducible promoters, and the cells were grown in the presence of increasing concentrations of IPTG.