Expression of MtrE by wild-type and mtr120 mutant strains. Expression of MtrE by wild-type and mtr120 mutant strains. Western blot analysis of whole-cell lysates from late-log-phase cultures was conducted using polyclonal rabbit MtrE-specific antibodies, followed by goat anti-rabbit IgG-alkaline phosphatase. Strain RD1 (44) contains a Kmr insertion in mtrE and was used as a negative control. The total protein from all strains was equally loaded, as assessed by Coomassie blue staining of a separate SDS-PAGE gel (data not shown). Elizabeth A. Ohneck et al. mBio 2011; doi:10.1128/mBio.00187-11