FIGURE 2.

Oxidized BigR ceases from binding to DNA and releases transcription. A, gel-shift assay showing that oxidized (S–S) BigR does not bind to the target DNA as reduced (S–H) BigR; however, binding is restored upon tris(2-carboxyethyl)phosphine (TCEP) treatment. Shifted bands are indicated by arrows, and FP is the free probe. B, gel-shift assay showing that both the C42S (M1) and the C108S (M2) mutants bind to the target DNA as the wild type (Wt) protein. Shifted bands are indicated by arrows, and FP is the free probe. C, GFP fluorescence as a measurement of the transcriptional activity of the bigR operon reporter plasmid alone (Rep) or in the presence of the wild type BigR, M1, or M2 proteins. D, GFP reporter gene assay of E. coli cell extracts expressing the wild type or mutated BigR proteins, in the presence (S–S) or absence (S–H) of GSSG. Error bars indicate S.E.