THE X-RAY STRUCTURE OF HUMAN SERUM CERULOPLASMIN AT 3.1 ANGSTROM - NATURE OF THE COPPER CENTERS

The X-ray structure of human serum ceruloplasmin has been solved at a resolution of 3.1 Angstrom. The structure reveals that the molecule is comprised of six plastocyanin-type domains arranged in a triangular a rray. There are six copper atoms; three form a trinuclear cluster site d at the interface of domains 1 and 6, and there are three mononuclear sites in domains 2, 4 and 6. Each of the mononuclear coppers is coord inated to a cysteine and two histidine residues, and those in domains 4 and 6 also coordinate to a methionine residue; in domain 2, the meth ionine is replaced by a leucine residue which may form van der Waals t ype contacts with the copper. The trinuclear centre and the mononuclea r copper in domain 6 form a cluster essentially the same as that found in ascorbate oxidase, strongly suggesting an oxidase role for cerulop lasmin in the plasma.