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. 2016 Mar 30;7:11072. doi: 10.1038/ncomms11072

Figure 7. Working model for the transport mechanism of group II ECF transporters.

Figure 7

Colours of the subunits as in Fig. 3. Starting with the complex trapped in the post-translocation state, binding of ATP is needed to release the empty S-component by disruption of the hydrophobic interface (red) (step (1)). The S-component will reorient to the outward-facing state (2) and can bind substrate on the extracellular side of the membrane (3). ATP hydrolysis in the ECF module regenerates the binding platform for the S-component (4). Possibly futile ATP hydrolysis takes place in this stage. The substrate-bound S-component can topple over in the membrane possibly aided by the vicinity of the ECF module (5). The toppled S-component binds to the ECF module via the complementary hydrophobic surfaces, coloured in red (6). Binding of the S-component to the ECF module forces the disruption of the substrate-binding site and release of the substrate into the cytoplasm.