Evidence for a Rieske-type FeS center in the thermoacidophilic archaebacterium Sulfolobus acidocaldarius.
A high-potential iron-sulfur cluster with characteristics similar to a Rieske-type center was detected in the plasma membrane of Sulfolobus acidocaldarius by EPR spectroscopy. In the reduced form this center has g-values of gz = 2.031, gy = 1.890 and gx = 1.725 (gav = 1.88, rhombicity = 0.37) and its reduction potential at pH 7.4 was determined to be +325 +/- 10 mV. The The archaebacterial cluster exhibits some unique properties, in comparison to eubacterial and eukaryotic Rieske-type centers. First, the reduction potential is pH-dependent in the range from pH 6.7 to 8.2. Second, the typical inhibitor of Rieske FeS centers, DBMIB, had no effect on the g-values of this cluster. The center is reducible by both NADH and succinate in the presence of cyanide, an inhibitor of the terminal oxidases. The possible role of a Rieske-type center in an organism lacking any c-type cytochromes is discussed.
Centro de Tecnologia Química e Biológica, Oeiras, Portugal.
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Anemüller
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Schmidt
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Schäfer
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Teixeira
D002462:Cell Membrane / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy; D006863:Hydrogen-Ion Concentration; D007506:Iron-Sulfur Proteins / Q000032:analysis*; D010084:Oxidation-Reduction; D016945:Sulfolobus acidocaldarius / Q000737:chemistry*
D007506:Iron-Sulfur Proteins