The PdpB C-terminus is localized to the periplasm. (a) The putative transmembrane domains of PdpB as predicted by TMHMM (aa 10–29 and 273–292). The locations of PhoA fusions and the C-terminal fragment used in two-hybrid analyses are indicated. (b) Francisella tularensis ssp. novicida strains U112 (wild type), KKF219 (DFPI), and KKF177 (ΔdotU) were transformed with pKEK1764 (expresses PdpB1–272-PhoA), pKEK1765 (expresses PdpB1–312-PhoA), pKEK1763 (expresses ΔN-Bla-PhoA), and/or pKEK1762 (expresses Bla-PhoA) and assayed for alkaline phosphatase activity. The assay was performed in triplicate. C. Whole-cell lysates from strains used in (b) were separated by 10% SDS-PAGE and subjected to Western immunoblot analysis with anti-PhoA (‘α-PhoA’) antibodies.