To that end, we have determined the structure of the Vag8 passenger domain in complex 97 with the C1-INH Serpin domain using single particle cryo-electron (cryo-EM) microscopy to complement regulatory control by a unique mechanism not previously seen in other pathogens. 102 Sequestration of C1-INH in this manner not only leads to complement evasion but also 103 promotes kallikrein activation, leading to increased levels of the vasoactive bradykinin, 104 increased fibrinolysis, and coagulation. Thus B. pertussis widely perturbs serum activities 105 across a broad spectrum by production of a single protein molecule. Table 1 ), mutation of multiple residues within the cleft to alanine was required to prevent 181 formation of the complex emphasising the extended nature of the interaction site (Figures 2,   182 3). 