Figure 1.

E. coli AcrB and AcrBZ in Saposin A Discs

(A) Structure of AcrB in saposin A discs prepared using E. coli lipids. Side (left; oriented so that the 3-fold axis is aligned vertically), periplasmic (center; along the 3-fold axis), and cytoplasmic (right; along the 3-fold axis) view. Within the trimer, the AcrB subunits are found in loose (L, navy blue), tight (T, blue), and open (O, cyan blue) conformations. Two DARPin domains (yellow) are positioned at the top of the periplasmic domain; attached to protomers in loose (L) and tight (T) conformations. The gray box indicates position of inner membrane.

(B) Structure of AcrBZ in saposin A discs in three views (see above). Two DARPin domains (yellow) are attached to protomers in L and T. AcrZ is displayed in red.