Formation of high-valent iron-oxo species in superoxide reductase: characterization by resonance Raman spectroscopy.

ABSTRACT

Superoxide reductase (SOR), a non-heme mononuclear iron protein that is involved in superoxide detoxification in microorganisms, can be used as an unprecedented model to study the mechanisms of O2 activation and of the formation of high-valent iron-oxo species in metalloenzymes. By using resonance Raman spectroscopy, it was shown that the mutation of two residues in the second coordination sphere of the SOR iron active site, K48 and I118, led to the formation of a high-valent iron-oxo species when the mutant proteins were reacted with H2O2. These data demonstrate that these residues in the second coordination sphere tightly control the evolution and the cleavage of the O-O bond of the ferric iron hydroperoxide intermediate that is formed in the SOR active site.