Fig 7.
ExsA activates transcription of Y. pestis transcriptional reporters. (A to C) The PA103 exsA::Ω strain carrying either the PyopN-lacZ (A), PyscN-lacZ (B), or PlcrG-lacZ (C) reporters was transformed with pJN105, pExsA, or pLcrF. The resulting strains were cultured under noninducing (−EGTA, open bars) or inducing (+EGTA, hatched bars) conditions for T3SS gene expression and assayed for β-galactosidase activity. Values were reported in Miller units. (D to F) EMSAs using radiolabeled probes derived from the LcrF-dependent PyopN (D), PyscN (E), and PlcrG (F) promoters. The PalgD probe was included in all binding reactions as a nonspecific (Non-Sp) control. Probes (0.05 nM each) were incubated in the absence (lane 2) or presence of 11, 23, 45, or 90 nM ExsA (lanes 3 to 6 in each panel) or LcrF (lanes 7 to 10 in each panel) for 15 min at 25°C. Samples were analyzed by native polyacrylamide gel electrophoresis and phosphorimaging. The positions of shift products 1 and 2 are indicated.