FIG 8.

The conserved histidine residues of EI^Ntr and NPr are required for their function. The levels of expression of two PmrA-regulated effector-encoding genes (ceg3 and lepB) were examined in the L. pneumophila ptsP deletion mutant (SY-ΔptsP) and the ptsO deletion mutant (SY-ΔptsO-Km). The bacteria contained a plasmid carrying the wild-type ptsP gene, the wild-type ptsO gene, the mutated ptsP^H371A gene, or the mutated ptsO^H15A gene cloned under the control of the IPTG inducible Ptac promoter. The plasmids containing the corresponding lacZ fusion of the examined gene without the ptsP or ptsO gene were used as controls (white bars). The IPTG concentrations used to express the wild-type and mutated ptsP genes were 0.005, 0.01, and 0.05 mM, and they were 0, 0.005, and 0.01 mM for ptsO. The levels of expression of the lacZ fusions were found to be significantly different (*, P < 0.001, Student's t test) in comparisons between results for the lacZ fusions containing the ptsP or ptsO gene expressed from the Ptac promoter and those for the fusions without the ptsP and ptsO genes. β-Galactosidase activity was measured as described in Materials and Methods. Data (expressed in Miller units [M.U.]) are the averages ± standard deviations (error bars) of the results of at least three different experiments.