After DNA sequencing, the activity of these mutant promoters was assayed in C. metallidurans CH34. Construction of the PpbrA −1 mutant Mutagenic PCR [38] of the 1144 bp pbrR-PpbrA-ΔpbrA DNA fragment from pMapbrR/PpbrA was used to construct the −1 promoter mutant of PpbrA, using the primers -1CentreEco and -1CenterBam to introduce the −1 deletion, and primers -1EcoPbr and -1BamPbr as flanking primers (Table 2). The PCR product containing the -1PpbrA promoter was digested with EcoRI and BamHI and subcloned into the multiple cloning site of pMU2385. The DNA sequence of the

pbrR-PpbrA-ΔpbrA DNA fragment containing the −1 deletion in PpbrA was confirmed, and this plasmid provided the mutant promoter for the assay in C. metallidurans AE104. β-galactosidase assays

in C. Metallidurans pMU2385 plasmid constructs were https://www.selleckchem.com/products/cx-5461.html electroporated into C. metallidurans, and cultures containing pMU2385 derivatives were assayed for ß-galactosidase activity as described in [39] with modifications described by [15]. Results PbrR binds to the LGX818 solubility dmso pbrA promoter and pb(II) decreases the binding affinity of PbrR to PpbrA in vitro PbrR was overexpressed as a thioredoxin-his Tag-S tag-fusion protein using the pET32-LIC expression system, purified and released after enterokinase digestion as untagged, full length PbrR, as described in Materials and Methods. The PbrR preparation was estimated as being >95% pure PbrR by Coomassie Blue staining of standard SDS-PAGE gels (data not shown). We had originally identified a candidate PpbrA promoter based on sequence similarity to other MerR family cAMP promters, and on run-off transcription studies of the pbr operon [4] and studied PbrR interactions with this Selonsertib in vivo region of the pbr operon. Initial PbrR gel retardation assays on 32P-end-labelled DNA from pUK21pbr1, which contained pbrR/PpbrA/ΔpbrA, had been digested with BstEII and NruI showed retardation only of the 282 bp

BstEII/NruI DNA fragment containing the previously identified PpbrA promoter region, and no other fragments from the plasmid (data not shown). Addition of PbrR to the end-labelled 296 bp PpbrA PCR product retarded this fragment, and addition of Pb(II) to PbrR and PpbrA increased the amount of PbrR required to retard the PpbrA DNA fragment (Figure 1A) indicating that PbrR-Pb(II) had a lower affinity in vitro with PpbrA than did apo-PbrR did, as is the case with MerR and Hg(II) (reviewed in [10]). PbrR protects the pbrA promoter from DNAse I digestion in vitro The 296 bp PpbrA PCR product described above was also used to determine the PbrR binding site on the promoter by DNase I protection assay. Figure 1B shows the autoradiograph of the PbrR DNase I footprint on PpbrA. The region protected by PbrR on PpbrA includes the −35 and −10 sequences as well as the 19 bp spacer containing an imperfect dyad symmetrical sequence between them, and is consistent with DNAse I protection results for MerR, CueR and ZntR [18, 20, 23, 24, 40].