FIGURE 6.

Assembled models of pumps. OMF subunits are shown as gold or orange shades except for the beta-barrel in the outer membrane and the equatorial domain, which are in gray. AcrB and CusA trimeric RND transporters are blue for its periplasmic domains, gray for its membrane domains. EmrA MFS transporter is in gray (a dimer is shown for size comparison). Adaptors are in shades of green or yellow around the OMF. (A) AcrABTolC model based on site specific cross-linking data (Symmons et al., 2009). Domains of the AcrB are distinguished by green shades. (B) CusBAC model based on the docking in Su et al. (2011). This is based on the maximum interpenetration without alteration in the CusB hairpin domains. Closer approach of the CusC and CusA is possible after re-alignment of the adaptor tips. (C) AcrABZTolC model based on fitting to single-particle CryoEM envelope (Du et al., 2014). The AcrZ subunit, to which one copy of AcrA was fused, is shown in light-blue. (D) EmrABTolC model suggested by the structure of Hinchliffe et al. (2014) and constructed by docking six EmrA subunits based on the arrangement of helices in the TolC trimer (Figure 5B). Further interpenetration would be possible after re-alignment of the adaptor tips.