The affinity of PmrA for its target promoters controls gene expression kinetics.

<p>(A–D) mRNA levels of the PmrA-activated <i>pbgP</i> (A, C) and <i>pmrC</i> (B, D) genes from isogenic <i>S. typhimurium</i> 14028s strains expressing either the <i>pmrA</i> (<i>G211</i>) gene (EG13404) or the <i>pmrA</i> (<i>E211</i>) gene (EG16279) (A, B) and from isogenic <i>S. typhimurium</i> Δ<i>pmrD</i> strains expressing either the <i>pmrA</i> (<i>G211</i>) gene (EG14088) or the <i>pmrA</i> (<i>E211</i>) gene (DC46) (C, D) determined by reverse-transcription-qPCR analysis. Bacteria were grown in medium containing 10 mM Mg²⁺, shifted to medium containing 10 µM Mg²⁺ and 100 µM Fe³⁺ and harvested at the designated times to prepare RNA. Expression levels were normalized to those of the 16S ribosomal RNA gene. Data correspond to at least three independent experiments and error bars show standard deviation.