Fig. 2.

The urease active site. The active site of urease contains two nickel atoms (green) bridged by a carboxylated lysine and a hydroxyl group. Ni1 is also coordinated by two histidine residues and a solvent molecule, while Ni2 is coordinated by two histidines, an aspartic acid residue, and a water molecule. Waters are red, metal-binding side chains are shown with white carbon atoms, and two nearby histidine residues that function in catalysis are shown with orange carbon atoms.