FIGURE 4.
CroSR391 trans‐regulation of RumABR391‐dependent mutagenesis. (a) Spontaneous histidine reversion mutagenesis assays utilizing MVG114 strains harboring pJM1378 alone (−/−), a pCC1 derivative (copy‐control plasmid) carrying the rumAB R391 operon, were transformed with low‐copy pGB2 derivatives (pJM1365, pJM1366, pJM1367, and pJM1368) carrying various iterations of the croS R391/setR R391 operon (Table 1). The genotypes of croS R391 or setR R391, either wild‐type or deleted, are indicated. (b) Western blot analysis using an anti‐CroS antibody indicating that only strains harboring a plasmid with a wild‐type croS R391 gene express any CroS protein. (c) Western blot using an anti‐RumA antibody indicating that strains that express the CroS protein have significantly reduced levels of the RumA protein. However, strains that express only SetR show no reduction in the level of RumA protein. Numbers reported for the levels of RumA and RumA′ are relative to RumA in track 1