Figure 3. Schematic showing methods for artificial imposition of electrochemical ion gradients in proteoliposomes.

The Δψ (interior positive), ΔpH (interior acidic), Δp (interior positive and acidic), Δψ_REV (interior negative), Δp_ΔψREV (interior negative and acidic), or ΔpH_REV (interior alkaline) were imposed by 100-fold dilution of proteoliposomes containing inside-out oriented MsbA-WT or MsbA-MD as described in the main text. Inclusion of DNA in the lumen allows the recording of the fluorescence emission of accumulated ethidium.