Fig. 4. The gate loop (g-loop) variations.

Structural and sequence level differences of g-loop are shown by highlighted loop structure and important residues of OqxB (A), AcrB (B), and MexB (C). Important hydrophobic residues which are crucial for substrate binding were highlighted as yellow color sticks and labeled. All the three structures were superimposed to emphasize the g-loop orientational differences of OqxB comparing with the other two structures (D). Sequences of g-loop aligned to highlight the extra residues of OqxB.