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. 2019 Nov 18;8:e51179. doi: 10.7554/eLife.51179

Figure 5. The rotor-stator interface is flanked by bound cardiolipin.

(A) View from the c-ring towards the membrane-embedded stator subunits. H5a and H6a are augmented by the tilted, amphipathic H1EG4 (brown). Cardiolipin molecules flanking subunit a are shown in red (tails of acyl chains are mostly disordered and shown only for illustration). Proton half-channels on the lumen and matrix side are shown in orange and red respectively. Remaining subunits not shown for clarity. The conserved R178 and the H186 at the lumen channel exit are shown with interacting residues. (B) Entrance of the lumenal channel (orange) is lined by the termini of subunit f, ATPEG4, subunit 8, ATPEG3, as well as a lumenal segment of subunit i/j. Inside the Fo, the lumen channel is confined by transmembrane helices of subunits f and b. β-DDM occupying the exit of the lumen channel shown in orange with density map as mesh, c-ring in grey. Arrows indicate proposed path of proton flow. (C) Polar and protonatable residues between R178 and the matrix-side half channel (red mesh). Subunit k contributes a horizontal helix (H1k) to the rotor-stator interface.

Figure 5.

Figure 5—figure supplement 1. Comparison between E. gracilis and S. cerevisiae rotor-stator interfaces.

Figure 5—figure supplement 1.

The E. gracilis ATP synthase (A,C) displays a larger rotor-stator interface than S. cerevisiae (B,D). (B) In yeast, the interactions (red) with the c-ring are mainly formed by the horizontal H5a and H6a in the membrane (green). (A) In E. gracilis, four horizontal helices (H5a, H6a, H1EG4, H1k) are found at the rotor-stator interface, with the H5EG1 forming a lumenal c-ring interaction. (C,D) Interactions between the Fo stator (grey) and the c-ring (white transparent) are highlighted in red.
Figure 5—figure supplement 2. Native phospholipids of the rotor-stator interface.

Figure 5—figure supplement 2.

Associated native phospholipids of the E. gracilis rotor-stator interface. (A) Top view of the rotor-stator interface. The offset half-channels are separated by the central R178 (lumenal channel with β-DDM shown in orange; internal end of matrix channel shown in red). The half channels are flanked on either side by a cardiolipin (shown in red). Species-specific structural elements constituting the rotor-stator interface near the matrix channel enclosed by dashed blue line. (F-H) Cardiolipins (B,C) and unidentified phospholipid (D) of the rotor-stator interface (map density shown in grey mesh).