Multiple weak interactions between BvgA~P and ptx promoter DNA strongly activate transcription of pertussis toxin genes in Bordetella pertussis.

Pertussis toxin is the preeminent virulence factor and major protective antigen produced by Bordetella pertussis, the human respiratory pathogen and etiologic agent of whooping cough. Genes for its synthesis and export are encoded by the 12 kb ptx-ptl operon, which is under the control of the pertussis promoter, Pptx. Expression of this operon, like that of all other known protein virulence factors, is regulated by the BvgAS two-component global regulatory system.

Novel architectural features of Bordetella pertussis fimbrial subunit promoters and their activation by the global virulence regulator BvgA.

A prominent feature of the promoters of Bordetella pertussis fimbrial subunit genes fim2, fim3 and fimX is the presence of a 'C-stretch', a monotonic run of C residues. The C-stretch renders these genes capable of phase variation, through spontaneous variations in its length. For each of these we determined the length of the C-stretch that gave maximal transcriptional activity, and found that the three optimized promoters align perfectly, with identical distances between conserved upstream sequences and the downstream -10 elements and transcriptional start sites.

Considerations in the development of live biotherapeutic products for clinical use.

Food products in the United States (U.S.), including dietary supplements, may contain live microorganisms and can be promoted for general health, nutritional, or structure/function claims.

Role of BvgA phosphorylation and DNA binding affinity in control of Bvg-mediated phenotypic phase transition in Bordetella pertussis.

To investigate the mechanism by which the Bordetella BvgAS phosphorelay controls expression of at least three distinct phenotypic phases, we isolated and characterized two B. pertussis mutants that were able to express Bvg- and Bvg(i) phase phenotypes but not Bvg+ phase phenotypes. In both cases, the mutant phenotype was due to a single nucleotide change in bvgA resulting in a single amino acid substitution in BvgA.

BvgA functions as both an activator and a repressor to control Bvg phase expression of bipA in Bordetella pertussis.

The Bordetella bipA gene is expressed maximally when the BvgAS phosphorelay is semi-active, i.e. in the Bvg-intermediate (Bvg(i)) phase.

Analysis of bvgR expression in Bordetella pertussis.

Bordetella pertussis, the causative agent of whooping cough, produces a wide array of factors that are associated with its ability to cause disease. The expression and regulation of these virulence factors are dependent upon the bvg locus, which encodes three proteins: BvgA, a 23-kDa cytoplasmic protein; BvgS, a 135-kDa transmembrane protein; and BvgR, a 32-kDa protein. It is hypothesized that BvgS responds to environmental signals and interacts with BvgA, a transcriptional regulator, which upon modification by BvgS binds to specific promoters and activates transcription.

The response regulator BvgA and RNA polymerase alpha subunit C-terminal domain bind simultaneously to different faces of the same segment of promoter DNA.

Examination of the binding of FeBABE-conjugated BvgA to the fha promoter of Bordetella pertussis has revealed that three dimers, formed by head-to-head association of monomers, bind one face of the DNA helix from the inverted-heptad primary binding site to the -35 region. The orientation of BvgA monomers within the dimers is the same as that recently demonstrated by X-ray crystallographic methods for a dimer of the C-terminal domain of NarL bound to DNA. Use of FeBABE conjugates of RNAP alpha subunit C-terminal domain showed that binding of this domain is linearly coincident with binding of the BvgA dimers, but to a different helical face.