FIG. 2.

InvB does not affect the transcription or translation of sopE. (A) Salmonella serovar Typhimurium carrying a sopE::lacZ transcriptional fusion (wild type) (8) and isogenic derivatives carrying a ΔinvB or ΔinvF (negative control) mutation were grown under SPI-1-TTSS-inducing conditions (5). The ΔinvF strain was included as a negative control since this transcriptional regulator controls the expression of SopE, and in its absence, expression of sopE is abolished(20). β-Galactosidase activities of whole-cell lysates of these strains were measured by using chemiluminescence as indicated by the manufacturer (Roche). Results represent the means ± standard deviations of three independent determinations. (B) A plasmid encoding a translational fusion of amino acids 1 to 38 of SopE to PhoA under the regulation of the native sopE promoter was introduced into wild-type Salmonella serovar Typhimurium or an ΔinvB isogenic derivative. Strains were grown under SPI-1-TTSS-inducing conditions (5), and the levels of the SopE_1-38-PhoA chimeric protein in whole bacterial cell lysates were examined by Western immunoblot analysis using a rabbit antibody directed against PhoA.