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J. Bacteriol., 11 1995, 6486-6491, Vol 177, No. 22
PE Boucher and S Stibitz
Regulation of virulence factor expression in Bordetella pertussis is
mediated by the BvgAS two-component regulatory system. Although previous
studies have demonstrated that the transcriptional regulation of the
filamentous hemagglutinin gene (fhaB) involves binding of the BvgA
activator directly to the fhaB promoter region, the mechanism of pertussis
toxin operon (ptx) regulation by BvgA has remained unclear. We demonstrate
in vitro the specific binding of BvgA to a region upstream of the ptx
promoter that encompasses a 20-bp directly repeated sequence (positions
-157 to -117) previously shown to be critical for BvgA-dependent
activation. This binding is strictly dependent on the phosphorylation of
BvgA, which can be obtained by incubation of BvgA with acetyl phosphate. By
DNase I protection studies, we demonstrate the synergistic binding of
BvgA-phosphate and purified Escherichia coli RNA polymerase to the ptx
promoter. In the presence of the polymerase holoenzyme, a greatly extended
footprint encompassing the region between -163 and the putative polymerase
binding site was observed. The implications of these observations for
pertussis toxin expression and regulation are discussed.
Copyright © 1995, American Society for Microbiology
Synergistic binding of RNA polymerase and BvgA phosphate to the pertussis toxin promoter of Bordetella pertussis
Department of Bacterial Products, Food and Drug Administration, Bethesda, Maryland 20892, USA.
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