Subcellular localization and immunological detection of proteins encoded by the vir locus of Bordetella pertussis

Abstract

The DNA sequence of the central regulatory locus vir of Bordetella pertussis predicts that three gene products, BvgA, BvgB, and BvgC, are encoded. Features of the predicted primary structures of these proteins and their homology to other two-component systems suggest that BvgA is located in the cytoplasm, BvgB is located in the periplasm, and BvgC spans the inner membrane. We have used gene fusions to the phoA and lacZ genes of Escherichia coli to investigate the subcellular localization and membrane topology of these proteins. PhoA fusion proteins were also purified and used to raise antibodies that allowed visualization of the vir-encoded polypeptides by Western immunoblotting. Our results have largely confirmed the predictions of the DNA sequence, with the exception that BvgB and BvgC were found to constitute one larger protein that was homologous to the sensor class of two-component systems. We propose that this protein be named BvgS (for sensor) and that its gene be named bvgS.