Sequences required for expression of Bordetella pertussis virulence factors share homology with prokaryotic signal transduction proteins.

The bvg locus of Bordetella pertussis is required for coordinate regulation of several factors associated with virulence. The control system is modulated by various environmental signals, including low temperature, MgSO4, and nicotinic acid. The nucleotide sequence of the bvg region has been determined and three open reading frames, bvgA, bvgB, and bvgC, are present. Twelve-base-pair linker insertion mutations in any of these open reading frames result in a Bvg- phenotype. The predicted protein products of bvgA and bvgC share homology with a family of prokaryotic regulatory proteins that respond to environmental stimuli and are members of two-component sensory transduction systems. We propose a model in which BvgB and the N-terminal portion of BvgC are localized in the periplasm. Environmental signals are recognized, transduced to the cytoplasmic portion of BvgC, and then transmitted to BvgA, a positive regulator of transcription.