Figure 2.
DksA variants D74N, D74E, and A76T, but not D71N, are defective for inhibition of rRNA transcription in vivo. The bars indicate the amount of transcription from a chromosomal rrnB P1-lacZ fusion in a strain lacking the dksA gene and containing a plasmid encoding either wild-type DksA (pDksA), the plasmid vector only (pINIII), or the indicated variant DksAs. Cells were grown in LB containing 0.1 mM IPTG and 100 ug/ml ampicillin to (A) mid-log (OD600 ~0.4) or (B) stationary phase (OD600 ~5.0). Bars represent the mean β-galactosidase activities and standard deviations from four independent cultures. Numbers above each bar indicate the fold-increase relative to the strain containing the pDksA plasmid under the same conditions. Western blots shown at the top of each panel indicate that the DksA levels in the strains with the D74N, D74E, and A76T variants were at least as high as in the strain with wild-type DksA.