Fig. 1.

Steady-state levels of ExbB mutants. Wild-type W3110 (WT), the parent strain for all of the plasmid variants (ΔexbBD ΔtolQRA), the parent plasmid encoding both ExbB and ExbD (pExbBD), and the plasmid-encoded ExbB variants are indicated above each lane of the immunoblot. Bacterial strains expressing plasmid-encoded ExbB variants were grown under conditions identical to those for the iron transport assays in Table 2. Samples with equal numbers of bacteria were precipitated with TCA, electrophoresed on 13% SDS-polyacrylamide gels, and immunoblotted with anti-ExbB antibody. ExbB monomer and proteolytic degradation products are labeled on the right. Positions of mass standards are indicated on the left.