Supplementary Material for: Vitronectin Binds to a Specific Stretch within the Head Region of Yersinia Adhesin A and Thereby Modulates Yersinia enterocolitica Host Interaction

Complement resistance is an important virulence trait of <i>Yersinia enterocolitica (Ye)</i>. The predominant virulence factor expressed by <i>Ye</i> is <i>Yersinia</i> adhesin A (YadA), which enables bacterial attachment to host cells and extracellular matrix and additionally allows the acquisition of soluble serum factors. The serum glycoprotein vitronectin (Vn) acts as an inhibitory regulator of the terminal complement complex by inhibiting the lytic pore formation. Here, we show YadA-mediated direct interaction of <i>Ye</i> with Vn and investigated the role of this Vn binding during mouse infection in vivo. Using different <i>Yersinia</i> strains, we identified a short stretch in the YadA head domain of <i>Ye</i>O:9 E40, similar to the ‘uptake region' of <i>Y. pseudotuberculosis</i> YPIII YadA, as crucial for efficient Vn binding. Using recombinant fragments of Vn, we found the C-terminal part of Vn, including heparin-binding domain 3, to be responsible for binding to YadA. Moreover, we found that Vn bound to the bacterial surface is still functionally active and thus inhibits C5b-9 formation. In a mouse infection model, we demonstrate that Vn reduces complement-mediated killing of <i>Ye</i> O:9 E40 and, thus, improved bacterial survival. Taken together, these findings show that YadA-mediated Vn binding influences <i>Ye</i> pathogenesis