Fig 6.

Autoregulation of mucR expression in Brucella abortus 2308. (A) β-Galactosidase activity produced by a mucR-lacZ transcriptional fusion. The activity of a mucR-lacZ transcriptional fusion was tested in B. abortus 2308, the mucR isogenic mutant strain (ΔmucR), and the mucR mutant complemented in trans (ΔmucR::pC³030). β-Galactosidase activity is shown as average Miller units ± standard deviations, and the results shown are from a single experiment that was repeated in triplicate. The asterisk indicates a significant difference in β-galactosidase activity between the parental strain 2308 and the mucR mutant strain (t test; P < 0.05). (B) Recombinant MucR (rMucR) protein was tested for binding to the mucR promoter region using an EMSA. Similar to the EMSA experiments in Fig. 3A, increasing concentrations of rMucR were incubated with radiolabeled DNA corresponding to the mucR promoter region, and in some binding reactions, unlabeled specific or nonspecific competitor DNA fragments were included as controls. The binding reactions were resolved in 6% native polyacrylamide gels and visualized by autoradiography.