Structures of Methylocystis sp. strain M pMMO subunits. (A) One of the three protomers in the trimer. The pmoB, pmoA, and pmoC subunits are shown in gray, blue, and purple, respectively. Copper ions are shown in cyan and a zinc ion is shown in gray. The additional helix is shown in yellow. (B) Overlay of the pmoA subunits from the Methylocystis sp. strain M (blue) and the original M. capsulatus (Bath) (gray) structures. (C) Overlay of the pmoC subunits from the Methylocystis sp. strain M (purple) and the original M. capsulatus (Bath) structures. (Reprinted with permission from Ref. 703. Copyright 2011 American Chemical Society.)