Fig. 1.

Schematics of the MotA/MotB, ExbB/ExbD, TolQ/TolR, and AglQ/AglR/AglS proton channels. The membrane topology of the involved proteins is shown in the context of the cell envelope. System specific components are indicated in gray. H⁺-flux (vertical red arrows) induced interactions that determine the system specific outputs are indicated by red arrows. For simplicity, the H⁺-flux in the AglQRS system is only shown to involve AglR and AglQ. For simplicity, the interactions between AglQRS and AglZ and between AglZ and MreB are shown as direct. For simplicity, all complexes are shown with 1:1 stoichiometries. The stoichiometry of MotAB is 4:2, with 11 to 12 complexes making up the full stator ring, of ExbBDTonB 7:2:1, of TolQRA 4–6:2:1, and of AglQRS it is not known.