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Figure 2.
Di-copper center in M. sexta PPO2. The active site of PPO2
can be superimposed well with that of oxygenated Limulus
polyphemus hemocyanin (Lp-HC, PDB ID code 1OXY). The secondary
structures of PPO2 are shown in the ribbon and colored in
yellow. The 6 copper-coordinating His ligands are shown as
sticks, with those from Lp-HC colored green. The di-copper atoms
are shown as spheres: PPO2, red; Lp-HC, purple. The peroxide ion
in Lp-HC is shown as brown spheres. Notice the unique E395 in
PPO2, which is located near the substrate place holder F88. E395
could be a base for phenol deprotonation, which is key to the
ortho-phenol hydroxylation activity of PPO.
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