Cobalt binding in 3QXE

Above is an excerpt from Figure 6C in "Evidence for Participation of Remote Residues...etc by Ondrechen and Ringe which very nicely shows how the cobalt ion is bound into a nitrile hydratase.  There are three sulphur based points of attachment- aC112, aC115 and aC117, the latter two as sulfinic acids and two amide nitrogen points of attachment, aS116 and aC117. It is really clearly shown in this view how the arginine bR52 preorganizes the sulfinic cysteines and amide nitrogens into a planar SSNN arrangement.