Structural and functional studies of BapC protein of Bordetella pertussis

Bordetella pertussis, the causative agent of whooping cough, attaches to mucosal surface in upper respiratory tract, where it produces a variety of surface associated and secreted autotransporter molecules among others. In this study we have cloned newly identified member of autotransporter family BapC (B. pertussis autotransporter protein C); expressed it in Escherichia coli and characterized it for its different properties. We have also raised antisera to BapC protein; the antisera were used in immunofluorescence assay to determine the surface association of the protein. Results suggest that BapC in B. pertussis Taberman parent is surface exposed when compared with the respective BapC mutant. The neutralizing effect of anti-BapC serum was also evaluated in the presence of active complement proteins and results suggest that antiserum can potentiate the killing of B. pertussis cells in the presence of added source of complement. Structure of the protein was also studied, both α and β domains of the protein were modeled, β domain exhibits typical transmembrane β-barrel porin topology whereas α domain behaves as a characteristic bacterial autotransporter passenger domain.