Figure 9.

Superimposition of each crystal structure of the CusBA-Cu(I) complex. (a) Superimposition of subdomains PC2 and TM8 of CusA. The 30° rotation of PC2 upon transition from the “pre-extrusion 1” state (blue), through the “pre-extrusion 2” state (green) to the “extrusion” (red) state is depicted by the black arrow. (b) Superimposition of subdomains PC1 and the horizontal helix of CusA. The C-terminal end of the horizontal helix is observed to rotate by 21° upon binding (gray, apo-CusBA; yellow, CusA-Cu(I); blue, form Ia; green, form II; magenta, form III). The C-terminal residues 391 to 400 of molecule 1 of CusB (orange) are also included. (c) Superimposition of TM5 and TM6 of CusA. Upon binding, these subdomains are observed to shift toward the periplasm by approximately one turn (gray, apo-CusBA; yellow, CusA-Cu(I); blue, form Ia; green, form II; red, form III). The structure of form Ib, which is nearly identical to that of form II, has not been included.