Fig. 1

Apo inward-facing and Mg²⁺•AMP-PNP-bound outward-facing structures of QTA CmABCB1. Anterior (a–d) and lateral (e, f) views of the QTA CmABCB1 structures in the inward- (a, b, e, f) and outward-facing (c, d, g, h) conformations are shown as cartoon representations (a, c, e, g) or as a cutaway surface representations of the TMDs with the interior shown in black (b, d, f, h). One subunit is colored, and the other is shown in gray. Secondary structure elements and amino acid residues belonging to the other subunit are indicated by asterisks in all figures. Horizontal black and gray bars represent the expected positions of the hydrophilic and hydrophobic surfaces of the lipid membrane, respectively. In b, f, d, h, the cross-section passes through a crystallographic twofold axis. NBDs are shown as outlines for simplicity. In c, d, g, h, bound Mg²⁺•AMP-PNP molecules at NBDs are shown as spheres