Fig 4.
ElrR specifically binds the elrA promoter region. (Top) Map of the intergenic region upstream of the E. faecalis elrA operon, with the ORFs elrR and elrA. The transcription orientation of elrA and elrR is indicated by thick arrows, and the thin arrow indicates the promoter of the elrA operon (PelrA). The lollipop indicates a 50-bp inverted repeat at the DNA level and the predicted transcription terminator. Lines below represent DNA probes used for EMSAs; numbers correspond to the location of the extremities relative to the start codon of the elrA gene. (Bottom) EMSA of elrA promoter region with ElrR. In the left panel, 3 ng of a 0.5-kb fluorescently labeled DNA fragment encompassing the upstream region of PelrA (S for “specific”) and 5 ng of a fluorescently labeled DNA control fragment (NS for “nonspecific”), corresponding to a 0.3-kb internal fragment of the elrR gene, were incubated with 0, 1, 1.5, and 2 μM purified ElrR (lanes 1 to 4, respectively). An excess of cold S (lanes 5 and 6) and NS (lanes 7 and 8) DNA probes was added to the binding reaction mixtures in the absence (lanes 5 and 7) or presence (lanes 6 and 8) of 1.5 μM ElrR. In the right panel, EMSA of DNA probes encompassing nested fragments of the PelrA region that were incubated without (−) or with (+) 1.5 μM ElrR. S and 1 to 4 correspond to the DNA probes shown on the map above.