ABC transporters belong to the ATP-Binding Cassette superfamily, which uses the hydrolysis of ATP to translocate a variety of compounds across biological membranes.

ABC transporters are involved in the export or import of a wide variety of substrates ranging from small ions to macromolecules.

Besides these two regions, three other conserved motifs are present in the ABC cassette: the switch region which contains a histidine loop, postulated to polarize the attacking water molecule for hydrolysis, the signature conserved motif (LSGGQ) specific to the ABC transporter, and the Q-motif (between Walker A and the signature), which interacts with the gamma phosphate through a water bond.

The hinge between armI and armII contains both the histidine loop and the Q-loop, making contact with the gamma phosphate of the ATP molecule.

In the dimer the two ABC cassettes contact each other through hydrophobic interactions at the antiparallel beta-sheet of armI by a two-fold axis.