title: Mössbauer study of the native, reduced and substrate-reacted Desulfovibrio gigas aldehyde oxido-reductase.
abstract: The Desulfovibrio gigas aldehyde-oxido-reductase contains molybdenum and iron-sulfur clusters. Mössbauer spectroscopy was used to characterize the iron-sulfur clusters. Spectra of the enzyme in its oxidized, partially reduced and benzaldehyde-reacted states were recorded at different temperatures and applied magnetic fields. All the iron atoms in D. gigas aldehyde oxido-reductase are organized as [2Fe-2S] clusters. In the oxidized enzyme, the clusters are diamagnetic and exhibit a single quadrupole doublet with parameters (delta EQ = 0.62 +/- 0.02 mm/s and delta = 0.27 +/- 0.01 mm/s) typical for the [2Fe-2S]2+ state. Mössbauer spectra of the reduced clusters also show the characteristics of a [2Fe-2S]1+ cluster and can be explained by a spin-coupling model proposed for the [2Fe-2S] cluster where a high-spin ferrous ion (S = 2) is antiferromagnetically coupled to a high-spin ferric ion (S = 5/2) to form a S = 1/2 system. Two ferrous sites with different delta EQ values (3.42 mm/s and 2.93 mm/s at 85 K) are observed for the reduced enzyme, indicating the presence of two types of [2Fe-2S] clusters in the D. gigas enzyme. Taking this observation together with the re-evaluated value of iron content (3.5 +/- 0.1 Fe/molecule), it is concluded that, similar to other Mo-hydroxylases, the D. gigas aldehyde oxido-reductase also contains two spectroscopically distinguishable [2Fe-2S] clusters.
authors.affiliation: Centro de Tecnologia Química e Biológica, Oeiras, Portugal.
authors.forename: B A
authors.initials: BA
authors.lastname: Barata
authors.forename: J
authors.initials: J
authors.lastname: Liang
authors.forename: I
authors.initials: I
authors.lastname: Moura
authors.forename: J
authors.initials: J
authors.lastname: Legall
authors.forename: J J
authors.initials: JJ
authors.lastname: Moura
authors.forename: B H
authors.initials: BH
authors.lastname: Huynh
mesh_terms: D000445:Aldehyde Oxidoreductases / Q000737:chemistry*; D003901:Desulfovibrio / Q000201:enzymology*; D004227:Dithionite / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy; D007501:Iron / Q000032:analysis; D008982:Molybdenum / Q000032:analysis; D010084:Oxidation-Reduction; D015204:Spectroscopy, Mossbauer; D013379:Substrate Specificity
chemical_list: D004227:Dithionite; D008982:Molybdenum; D007501:Iron; D000445:Aldehyde Oxidoreductases