The copper is tetrahedrally coordinated by a cysteine, 2 histidines, and a glutamine residue. Both histidines coordinate with copper through 3-nitrogen. The zinc coordination sphere is composed of three histidines, one aspartate and two water molecules. The catalytic zinc is coordinated by three histidines from the conserved HEXXHXXGXXH binding motif. The second motif has two histidines and is involved in metal ion binding.