Figure 1.

(a) A pairwise sequence alignment of AcrA and AcrE of S. enterica highlighting their predicted close structural homology. The top secondary structure is derived from the previously reported homology model of AcrE,²¹ while the bottom secondary structure corresponds to the experimental AcrA structure from E. coli (PDB ID 5O66; chain G), which has no sequence gaps with the AcrA of S. enterica. (b) Mapping the sequence differences between the Salmonella AcrE and AcrA onto the homology model of the AcrE.²¹ The non-conserved substitutions are shown in sidechain and semi-transparent sphere representation. The mapping demonstrates that the bulk of the discrepancies, which may be expected to account for the functional differences between the PAPs, map to their β-barrel and membrane-proximal domains. This figure appears in colour in the online version of JAC and in black and white in the print version of JAC.