BapC autotransporter protein of Bordetella pertussis is an adhesion factor

Bordetella pertussis, the causative agent of whooping cough, attaches to mucosal surfaces in upper respiratory tract, where it produces, a variety of surface-associated and secreted molecules. Among various secreted products, some of the proteins belonging to autotransporter family; pertactin (Prn), bordetella resistance to killing (BrkA) and a newly identified member, bordetella autotransporter protein-C (BapC), are investigated in this study for their adherence potential to various respiratory and non-respiratory tract specific cell lines. Our results reveal that BapC and Prn mutants adhere significantly less (p < 0.0001 and p < 0.05) respectively to human non-respiratory (HeLa-229) and murine macrophages (P-388 D-1) cells compared to their wild-type strains. Prn, BrkA and BapC share no homology in their passenger domains except existence of common motifs arginine-glycine-asparctic (RGD) and glycosaminoglycan binding site (SGXG). We have shown that RGD and SGXG motifs are present in the coiled region in Prn and BrkA proteins with the exception in BapC where R (463) of RGD and S (597) of SGXG motif were observed in beta sheet of the modeled protein structures. Therefore, there is possibility that such arrangement of motifs can confer greater probability of BapC in better selective adherence to binding sites on the HeLa-229 and P-388 D-1 cell lines.