Comparison of apo and holo states derived from the various independent datasets. (A) Overlay of density maps from C2 symmetric conformations from SP1, SP3sym, and SP4sym datasets. There is a 90° rotation between the two views and viewing angles in B, C, and D are indicated by arrows. (B) Close-up view of Zn binding site A from the three datasets. Density is visible at the site in SP1 and SP3sym maps but absent from the SP4sym map. (C) Comparison of site C in the CTD shows that extra density is present at site C in maps from SP1 (solid cyan surface) and SP3sym (mesh surface), consistent with the presence of metal ions; however, these densities are much weaker in the SP4sym map (solid blue surface). (D) Comparison of site B in the TM2/TM3 loop shows that the loop is ordered and that density associated with a metal ion is present in all three maps. (E) Overlay of density maps from the asymmetric conformations from SP2, SP3bent, and SP4bent datasets. There is a 90° rotation between the two views and viewing angles of F and G are indicated by arrows. (F) Close-up view of Zn binding site A from the three datasets. All density maps show a lack of density at the Zn site A. (G) Comparison of site C in the CTD shows a lack of density associated with metal ions in SP2 (solid purple surface) and SP4bent datasets (plum mesh); however, extra density is seen at this site in the map from SP3bent dataset (dark red mesh). Density for the TM2/TM3 loop and Zn site B is not shown because it is completely absent in these maps.