Fig 1.

(a) Schematic representation of the ser₂₀₀₃ gene locus, promoter region, and DNA fragments used in the gel mobility shift assays; the numbers indicate the ends of the fragments relative to the transcriptional start site. Direct repeats (DRs) and inverted repeats (IRs) are indicated; −10 and −35 hexamers, the transcriptional starting site (TSS), and the ribosomal starting site (RBS) are underlined. (b and c) Electrophoretic mobility shift assays carried out using ser₂₀₀₃ promoter fragments and cell crude extracts containing the full SerR protein (b) or its 5′-truncated fragment SerR-T (c). Gradients correspond to 2, 1, 0.5, and 0.25 μg of protein content. Cell extract from E. coli harboring the empty vector pQE30 was used as a negative control.