Functional dissection of type I and type II Ca²⁺-binding sites.

<p>SiiE was mutated in 5 consecutive BIg domains in the N-terminal (BIg1-5) or C-terminal (BIg47-52) region in 10 Ca²⁺-binding sites (D10), 5 type I Ca²⁺-binding sites only (Δ5_typeI), or 5 type II Ca²⁺-binding sites only (Δ5_typeII). A) Schematic overview of D/S exchanges introduced for deletion of Ca²⁺-binding sites in BIg1-5 or BIg 47–52. B) Western blot for analyses of synthesis of mutant forms of SiiE. C) Amounts of SiiE retained on the bacterial surface at 3.5 h, 6 h, 8 h and 24 h of subculture. D) Amounts of SiiE secreted in culture supernatant after 3.5 h and 6 h of subculture. E) SiiE-dependent invasion of polarized epithelial MDCK cells. Analyses of synthesis, surface retention and secretion and SiiE-dependent invasion of polarized cells were performed as described for <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1006418#ppat.1006418.g002" target="_blank">Fig 2</a>.