title: Spectroscopic studies of the nature of the iron clusters in the soluble hydrogenase from Desulfovibrio desulfuricans (strain Norway 4).
abstract: 57Fe-enriched samples of the soluble hydrogenase from Desulfovibrio desulfuricans (Norway) have been investigated in both the native (oxidized) and the dithionite-reduced states using Mössbauer spectroscopy. The data clearly show that the iron in this enzyme is predominantly in the form of iron-sulphur clusters which are closely similar to the [4Fe-4S] clusters found in a large number of ferredoxins, such as that from Bacillus stearothermophilus. There appear to be two [4Fe-4S] clusters. The iron-sulphur clusters in the oxidized protein are virtually diamagnetic, as indicated by Mössbauer, electron spin resonance and magnetic circular dichroic spectroscopy. On reduction by dithionite + methyl viologen, Mössbauer spectroscopy showed that only 50% of the [4Fe-4S] clusters were reduced. Even reduction with hydrogen up to a pressure of 23 GPa did not reduce the iron-sulphur clusters completely. An ESR signal due to a rapidly relaxing species with g = 2.03, 1.89 was observed in the reduced protein, together with a weaker spectrum from a slower-relaxing species at g = 2.34, 2.12.
mesh_terms: D055598:Chemical Phenomena; D002621:Chemistry; D002942:Circular Dichroism; D003901:Desulfovibrio / Q000201:enzymology*; D004578:Electron Spin Resonance Spectroscopy; D006864:Hydrogenase / Q000302:isolation & purification*; D007501:Iron / Q000032:analysis*; D010084:Oxidation-Reduction; D012995:Solubility; D013057:Spectrum Analysis / Q000379:methods
chemical_list: D007501:Iron; D006864:Hydrogenase