Crystal structure of the C47S mutant of human peroxiredoxin 5

In the crystal structure of the reduced form of the wild-type human peroxiredoxin 5, the
presence of a benzoate ion in direct interaction with the peroxidatic cysteine (Cys 47) appeared
as a rather intriguing feature since it is known that the benzoate ion can play the
role of a specific hydroxyl radical scavenger. The crystal structure of the C47S mutant of
the same enzyme has been crystallized in the tetragonal system, space group P41212, with
a = 65.65 Å, c = 122.04 Å. It confirms the presence of this benzoate ion in spite of the
mutation into a serine of the Cys 47 residue to which the benzoate ion was directly linked
in the wild-type structure. The benzoate ion seems to be stabilized by hydrophobic contacts
on both sides of the aromatic ring. In this matter, the α5 helix, which is specific to peroxiredoxin
5 among mammalian peroxiredoxins, plays an important role. These hydrophobic
contacts also allow to suggest why the benzoate ion disappears when the molecule is
oxidized.