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Figure 2.
Fig. 2. The binding sites for the four ligands. Amino acid
residues within 6 Å of the bound ligand molecules are
shown. With the exception of (C), the view is approximately from
the top (periplasmic side) of the trimer. Unmarked, primed, and
double-primed residues, respectively, belong to the three
subunits of the AcrB trimer. (A) R6G-binding site. (B)
Et-binding site, including Phe^388 that is slightly farther away
(see text). (C) Dq-binding site. The side view shows the binding
of the two quinolinium moieties within each Dq molecule (as in
Fig. 1). The phenylalanine residues interacting with the bottom
quinolinium moieties are shown even though they are 6.3 Å
away from the ligand. Ile^102 is not shown to avoid cluttering
the figure. (D) Cip-binding site.
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