Figure 2. ATP promotes gene transcription in a manner dependent on conserved A nucleotides in the mgtCBR leader region.

a, Fold change in fluorescence produced by an adenine auxotroph (EG9652) harboring the plasmid vector pfpv25, pGFP303 or derivatives with substitutions of conserved A nucleotides at position 44-46 by Ts (pGFP303 A_44-46→T), Gs (pGFP303 A_44-46→G), or Cs (pGFP303 A_44-46→C), with substitutions of conserved 55-56 A nucleotides by Gs (pGFP303 A_56-57→G), or with substitution of most of the mgtM sequence except for A nucleotides at 44-46 and 55-56 (pGFP303 mgtM_scrambled). Plasmid pfpv25mgtA harbors a transcriptional fusion between the PhoP-dependent mgtA promoter and mgtA leader sequence and a promoterless gfp gene. Bacteria were grown in N-minimal media with 10 μM Mg²⁺ in the presence of either 25 μM (low) or 250 μM (high) adenine. Fluorescence was monitored as described in Methods. Fold change was calculated by dividing the fluorescence of cells grown in the high adenine by that of cells grown in low adenine. Note that the ratio of fluorescence displayed at high and low adenine is the same for bacteria harboring pfpv25mgtA or the vector pfpv25. Data correspond to a representative of four independent experiments conducted in duplicate. b, Intracellular ATP levels and intracellular pH of purB Salmonella (EG9652) grown in the presence of the indicated concentrations of adenine were determined by labeling with ³²P-phosphorus and then separating by TLC. c, Fluorescence produced by wild-type Salmonella (14028s) harboring pGFP303 or pGFP303 A_44-46→T following growth for 4 h in N-minimal media with 10 μM Mg²⁺ in the presence of either 38 mM glycerol (~0.35%) or 0.2% glucose as a carbon source. d, Intracellular ATP levels of cells grown in the indicated carbon sources to an OD₆₀₀: 0.419 were determined by luminescence as described in Methods. Shown are the mean and SD from two independent measurements. e, Fluorescence produced by wild-type (14028s), mgtC (EL4), mgtB (EL5) and mgtA (EG9521) Salmonella harboring the vector (pfpv25), pGFP303, or its derivative pGFP303 A_44-46→T following growth for 4 h in N-minimal media with 10 μM Mg²⁺.