Plastocyanin Protein (inactive form)

Plastocyanin, also called blue copper protein, is a copper-containing protein involved in electron-transfer:
http://en.wikipedia.org/wiki/Plastocyanin

The model is of the reduced form of plastocyanin at low pH (3.8). The Cu(I) ion is trigonally co-ordinated by N(His37), S(Cys84) and S(Met92). The fourth Cu-ligand bond is broken. This form of the protein is redox-inactive.

Model of Plastocyanin from Poplar based on the Protein Data Bank entry 6PCY:
http://www.rcsb.org/pdb/explore/explor