Thesis presented January 19, 2001
Abstract:
Rubredoxin oxidoreductase (Rbo), also called desulfoferrodoxin (Dfx) is a 2 x 14 kDa homodimeric protein, found in some sulfate-reducing bacteria (Desulfovibrio spp.) and archaea. It contains two non-heme iron centers in each subunit, a rubredoxin-type center and a [Fe(NHis)4(SCys)] center. All experiments (SOD assay, reactivity study with O2.-, gamma radiolysis) have shown that the iron center [Fe(NHis)4(SCys)] is responsible for the enzyme superoxide reductase activity (SOR). A pulse radiolysis study has shown two intermediate species that could correspond to iron-peroxo species. Moreover, two mutants of residues in the vicinity of the SOR active site have been studied: the residue glutamate 47 mutated into alanine, and the residue lysine mutated into isoleucine. The Lys-Ileu mutant is 20 less active towards O2.- than the wild-type protein, and the Glu-Ala mutant could stabilize an iron-peroxo species during catalysis. Another class of SOR has been studied, from Trepanosoma pallidum, a microaerophile bacteria which doesn't contain SOD nor catalase. This SOR class doesn't possess the rubredoxin type center, and the protein contains the same activity. This SOR activity thus could represent a new strategy in the fight against superoxide stress.
Keywords:
Superoxide, oxidative stress, mononucléaire de fer, rubredoxin, iron-peroxyde, pulse radiolysis, hydrogen peroxide, anaeroby