Coordination environment and fluoride binding of type 2 copper in the blue copper oxidase ceruloplasmin

The electron paramagnetic resonance (EPR) spectra of the blue copper oxidase ceruloplasmin [ferroxidase, iron (II):oxygen oxidoreductase, EC 1.16.3.1] and of a derivative having the type I (blue) copper centers reversibly bleached are reported. The EPR spectrum of bleached ceruloplasmin has a seven-line superhyperfine structure in the g : formula: (see text) region that is attributed to the presence of three nitrogen-donor type 2 copper ligands. The EPR data suggest further that the type 2 copper in ceruloplasmin possesses a tetragonal coordination gometry. In the presence of varying amounts of fluoride, superhyperfine splitting patterns in the g : formula: (see text) region of both ceruloplasmin derivatives indicate that a maximum of two fluorides may be bound to the type 2 copper.