Fig. 7: Model of transport mechanism.
From: Rhodamine6G and Hœchst33342 narrow BmrA conformational spectrum for a more efficient use of ATP
A In absence of substrate, BmrA WT in the IF conformation is very plastic. The 2 NBS bind 2 ATP-Mg2+ (yellow oval) identically, leading to the OF conformation. Plastic deformation is transferred to the other side of BmrA for release of a potential substrate; return to the IF conformation is achieved via ATP hydrolysis and release of ADP-Mg2+ (orange oval). The white letters A,B,C,A’,B’,C’ refer to the Walker A, Walker B and signature C motifs of ABC transporters in the NBD. A NBS is formed by binding ATP between notably the A and B motifs of one NBD, and the C motif of the other NBD. B In presence of substrate, flexibility of the IF conformation is reduced and symmetrical closing is prevented by the presence of the drug. Binding of the first ATP-Mg2+ occurs by deformation around the drug, leading to the formation of the first NBS, which increases affinity for the other NBS and formation of the OF conformation. Using plasticity of the OF side of BmrA, substrate is released and the initial pathway of ATP hydrolysis is used to reset to the IF conformation.
