Fig. 2.

DARPins interact with the AcrB L and T monomers only (8). (Left) Side view of the AcrB trimer (with monomers L (loose, access) in blue, T (tight, binding) in yellow, and O (open, extrusion) in red, in complex with DARPins (light orange) and AcrA (green). Only the membrane-proximal (MP), the β-barrel, and the lipoyl domains of AcrA are shown, whereas the α-helical hairpin following the lipoyl domain has been omitted. (Right) Top view on the AcrB periplasmic porter domain with its subdomains PN1, PN2, PC1, and PC2. Shown is the interaction of AcrA with the AcrB PN2 and PC1 porter domains.