Structural and functional studies of rubrerythrin from desulfovibrio vulgaris
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Rubrerythrin (Rbr), found in anaerobic or microaerophilic bacteria and archaea, is a non-heme iron protein containing an oxo-bridged diiron site and a rubredoxin-like [Fe(SCys)4] site. Rbr has NADH peroxidase activity and it has been proposed as one of the key enzyme pair (Superoxide Reductase/Peroxidase) in the oxidative stress protection system of anaerobic microorganisms. In order to probe the mechanism of the electron pathway in Rbr peroxidase reaction, X-ray crystallography and rapid reaction techniques were used. Recently, the high-resolution crystal structures of reduced Rbr and its azide adduct were determined. Detailed information of the oxidation state changes of the irons at the metal-binding sites during the oxidation of Rbr by hydrogen peroxide was obtained using stopped-flow spectrophotometry and freeze quench EPR. The structures and activities of Rbrs with Zn(II) ions substituted for iron(III) ions at different metal-binding sites, which implicate the influence of positive divalent metal ions to the Rbr, are also investigated. The molecular mechanism for Rbr peroxidase reaction during the turnover based on results from X-ray crystallography and kinetic studies is proposed.