Figure 4

Alignment among 1esoA, 1oezZ, 1e9qB and 1uxlB, four structures associated with the same active site of Cu,Zn superoxide dismutase (EC code 1.15.1.1). The proteins are represented as strands and the active sites as sticks. 1esoA is pink, 1oezZ is green, 1e9qB is orange and 1uxlB is blue. The corresponding zinc ions are represented as balls (yellow for 1esoA and purple for 1eozZ). The seven-residue insertion of 1esoA (K54^A-A54^G) is red. The caret symbol (^) indicates an insertion code in PDB format, which reveals that these seven residues were discovered later after the first submission of 1esoA to PDB. All four structures share a histidine (H63 of 1esoA). The second histidine (H44 of 1esoA) only appears in 1esoA and 1e9qB, while the third histine (H80 of 1oezZ) only appears in 1oezZ and 1uxlB.