Fig. 6: Two asparagine/arginine pairs guide substrates ADP and ATP to and away from the central binding site as part of the transport cycle.

Lateral views from the membrane of the cytoplasmic-open state (left) (ScAac2, PDB code 4c9h chain A) and matrix-open state (PDB code 6gci chain A) (right) of the mitochondrial ADP/ATP carrier. The interacting residues of ScAac2 are conserved in TtAac and to facilitate comparison we used the TtAac labelling (Supplementary Fig. 3). The water-accessible surfaces, determined by HOLE59, are shown in transparent blue. Residues of the water-filled cavity that have critical and important roles in substrate binding are represented in red and orange, respectively, while the substrates ADP and ATP are shown in green and cyan, respectively. The water-accessible surfaces are shown in blue.