The transport activity of the multidrug ABC transporter BmrA does not require a wide separation of the nucleotide-binding domains

Conformational changes of the ABC Transporter BmrA Depend on Membrane Curvature

“…Regarding the open conformation, a wide range of openings have been reported among ABC exporters, with NBDs in close contact up to NBD separated by about 6-7 nm 14,16,23,46 . Our smFRET data in vesicles are consistent with the recent 3D model of BmrA in detergent 22 with dissociated NBDs in the apo form. Furthermore, we have shown that the opening of the apo form is independent of the liposome curvature (since the low FRET value does not change between LV and SV), in contrast with the transition rate between both conformations.…”

“…This demonstrates the co-existence of two states: i) a high FRET peak at <E app > = 0.45, corresponding to the closed state with an interdye distance of about 4 nm from known structures 19 (Supplementary Fig. S1); ii) a low FRET <E app > = 0.10, corresponding to an open conformation where the NBDs are separated about 7 nm according to the recent structure 22 . From the two-Gaussian fit, we extracted the respective weight of the low and high-FRET populations; we found that they have the same weight for both LV and SV, around 50% (Table 2).…”

“…A very recent cryo-EM structure of BmrA in detergent confirmed that the apo conformation is indeed open with dissociated NBDs, 2.6 nm away with respect to the closed form and a conicity of 28° (π/7) (Supplementary Fig. S1C) 22 . Altogether, we expect that substantial conformational changes of individual BmrA within the membrane will lead to local membrane deformations, dependent on its conicity during its ATP cycle.…”