Identification of the minimum region of Bordetella pertussis Vag8 required for interaction with C1 inhibitor.

An autotransporter of Bordetella pertussis, virulence-associated gene 8 (Vag8), binds and inactivates the complement regulator, C1 inhibitor (C1-Inh), and plays a role in evasion of the complement system. However, the molecular interaction between Vag8 and C1-Inh remains unclear. Here, we localized the minimum region of Vag8 required for interaction with C1-Inh by examining the differently truncated Vag8 derivatives for the ability to bind and inactivate C1-Inh. The truncated Vag8 containing amino-acid residues 102-548, but not 102-479 and 202-648, showed the full activity of intact Vag8, suggesting that the separate 102-202 and 548-648 amino-acid regions of Vag8 mediate the interaction with C1-Inh.