Fig 5.

ExbB S34A and W38A reduce the TonB-ExbB formaldehyde cross-linked complex. ExbB TMD1 mutants were expressed at chromosomal levels in strain RA1017 (ΔexbBD ΔtolQRA), and parent strain W3110 (WT) served as the wild-type chromosomal control. The strain or mutations are indicated above the lanes. Cultures grown to mid-exponential phase were cross-linked with monomeric formaldehyde and solubilized in gel sample buffer at 60°C. Samples were resolved on 11% SDS-polyacrylamide gels and immunoblotted with anti-TonB antibody. The positions and compositions of complexes are indicated to the right of the blot. The positions of molecular mass standards (in kilodaltons) are indicated to the left of the blot. A shorter exposure of the same immunoblot is shown in the bottom blot for comparison of monomer levels.