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Figure 5
Cyt b in samples of CIII2 prepared with antimycin A (a, c), oxidized with ferricyanide (b) or reduced with ascorbate (d). (a) Density for Trp142 (dashed ellipse) of the cd1-helix and Ile269 of the ef-loop was missing in maps of CIII2 with only antimycin A added when the Rieske domain (cropped out, residual yellow density) was in the intermediate position. Additional density was visible at a position near the Qo site on the left of the cd1-helix, partially overlapping with the position of Ile269 of the ef-loop (arrow). Densities for Val146, Ileu147, Cys148 and Asn149 were ambiguous as in the apo sample (Supplementary Fig. S7). (c) With the Rieske domain in the b position, density for Trp142 was resolved in the expected position beneath the ef-loop, as in samples with added ferricyanide (b), ascorbate (d), DQH2 or DQ. All side chains of the ef-loop and cd1-helix were also resolved with the Rieske domain in the intermediate position. The overall resolutions of the maps were 3.0 Å (a), 3.0 Å (c), 2.3 Å (b) and 3.2 Å (d). In the apo sample, density for Trp142 was also weaker when the Rieske domain was in the intermediate position (Supplementary Fig. S7).

ISSN: 2052-2525