Fig. 4.

A single nucleotide exchange protects sopD2 from targeting by SgrS. (A) Graphical presentation of predicted SgrS–sopD2 interaction. The vertical arrow denotes the U to C change in the sopD2* allele. (B) Graphical presentation of the SgrS–ptsG interaction. The vertical arrow denotes the C to U change in the sopD** allele. (C) Western and Northern blot analyses of strains harboring a chromosomal sopD2::3×FLAG allele transformed with a control plasmid (lanes 1–7) or the pP_L-SgrS plasmid (lanes 8–14). Samples were collected at the indicated time points of growth in rich media or under SPI-1– and SPI-2–inducing conditions, and were subjected to Western and Northern blot analyses. Regulation of the SopD::3×FLAG is shown for comparison. (D) Quantitative Western blot analysis of sopD::gfp, sopD2::gfp, sopD2*::gfp, and sopD**::gfp reporters combined with a control vector or pP_L-SgrS. Salmonella (ΔsgrS) double transformants were grown in rich media to OD₆₀₀ of 2.0, and total protein samples were subjected to Western blot analysis of GFP protein. Relative GFP expression was calculated from the average of three independent experiments. The standard deviation is indicated by error bars.