Figure 1
From: Modulation of the Neisseria gonorrhoeae drug efflux conduit MtrE
(a) Overall structure of the trimeric MtrE efflux protein channel (PDB code: 4MT0). Each subunit consists of a β-barrel domain, embedded in the outer membrane, an α-barrel domain, spanning ~ 100 Å inside the periplasm and an equatorial domain, mostly unstructured, located in the middle of the α-barrel. (b) The reported crystal structure of MtrE corresponds to a conduit with a comparably large cross-sectional area, in which the major constriction site is located at the tip of the periplasmic domain (110–120 Å from the extracellular exit along the pore axis). (c) The narrowest site in the channel is formed by two concentric aspartate rings comprising three D422 and D425 in the trimer (conserved across the other characterized OMPs), which are thought to act as a selectivity gate. Viewed from the periplasmic entrance, the ring formed by D422 is more proximal, the one from D425 more distal.
