Fig. 5.

ExbD disulfide-linked dimers increase in the absence of TonB. TCA-precipitated samples of wild-type chromosomally encoded ExbD (W3110) and a ΔexbD ΔtolQR strain (RA1045) or a ΔexbD ΔtolQR ΔtonB strain (KP1509) expressing plasmid-encoded ExbD Cys substitutions near native ExbD levels (see Table S1 in the supplemental material for induction levels) were resolved on nonreducing or reducing 15% SDS-polyacrylamide gels and immunoblotted with ExbD-specific polyclonal antibodies. Reduced and nonreduced samples came from the same culture. + indicates the presence (RA1045), and − indicates the absence (KP1509) of TonB. ExbD Cys substitutions are indicated across the top. The positions of nonreducing molecular mass standards are indicated on the left. d indicates the position of the homodimer, and m indicates the position of the monomer. The middle set of immunoblots is a shorter exposure of the top set showing the monomer band only.