Figure 2.

ToxR–TonB is conformationally responsive to pmf. Strains were converted to spheroplasts and treated with or without proteinase K and CCCP as described in Section “Materials and Methods” with the following strains: cTonB (W3110 expressing chromosomally encoded TonB) and pToxR–TonB [KP1344 (ΔtonB)/pKP1529]. l-Arabinose was added to induce expression of ToxR–TonB to chromosomal levels (0.00046%). Samples were resolved on 13% SDS-polyacrylamide gels, and immunoblotting was performed with the α-TonB monoclonal antibody 4F1. Mass standards are shown on the left. Abbreviations: WC, whole cells; Sph, spheroplasts; PKRF, proteinase K-resistant fragment.