Structural analysis of the mutations at N189, T678, Q737 and M844 (PDB ID: 2DHH). The “Access” conformation of the structure was used. In (a), N189 and Q737 (in blue) are near the hairpins (in red) that interact with TolC to form the AcrB-TolC complex. Q737 is in the vicinity of a hairpin on the adjacent protomer (in dark gray). In (b), T678 and M844 are shown in blue. Residues that were reported to be in the substrate path leading to the binding pocket are colored yellow [24, 25]. The amino acids F682, V716 and I827 (shown in pink) are in close proximity to M844 and flank residues in the substrate path (D681, R717 and L828). M844 is also on the same α-helix as E842 (shown in green) which is part of the vestibule leading to the binding pocket.