The quinol:fumarate oxidoreductase from the sulphate reducing bacterium Desulfovibrio gigas: spectroscopic and redox studies.
The membrane bound fumarate reductase (FRD) from the sulphate-reducer Desulfovibrio gigas was purified from cells grown on a fumarate/sulphate medium and extensively characterized. The FRD is isolated with three subunits of apparent molecular masses of 71, 31, and 22 kDa. The enzyme is capable of both fumarate reduction and succinate oxidation, exhibiting a higher specificity toward fumarate (Km for fumarate is 0.42 and for succinate 2 mM) and a reduction rate 30 times faster than that for oxidation. Studies by Visible and EPR spectroscopies allowed the identification of two B-type haems and the three iron-sulplur clusters usually found in FRDs and succinate dehydrogenases: [2Fe-2S]2+/1+ (S1), [4Fe-4S]2+/1+ (S2), and [3Fe-4S]1+/0 (S3). The apparent macroscopic reduction potentials for the metal centers, at pH 7.6, were determined by redox titrations: -45 and -175 mV for the two haems, and +20 and -140 mV for the S3 and SI clusters, respectively. The reduction potentials of the haem groups are pH dependent, supporting the proposal that fumarate reduction is associated with formation of the membrane proton gradient. Furthermore, co-reconstitution in liposomes of D. gigas FRD, duroquinone, and D. gigas cytochrome bd shows that this system is capable of coupling succinate oxidation with oxygen reduction to water.
Lemos
Rita S
RS
Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Oeiras, Portugal.
Gomes
Cláudio M
CM
LeGall
Jean
J
Xavier
António V
AV
Teixeira
Miguel
M
D003573:Cytochrome b Group; D003580:Cytochromes / Q000378:metabolism; D003901:Desulfovibrio / Q000201:enzymology*; D003902:Detergents; D004578:Electron Spin Resonance Spectroscopy; D004579:Electron Transport; D045222:Electron Transport Chain Complex Proteins; D029968:Escherichia coli Proteins; D006863:Hydrogen-Ion Concentration; D007506:Iron-Sulfur Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D007700:Kinetics; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D010101:Oxygen Consumption; D013057:Spectrum Analysis
D003573:Cytochrome b Group; D003580:Cytochromes; D003902:Detergents; D045222:Electron Transport Chain Complex Proteins; D029968:Escherichia coli Proteins; D007506:Iron-Sulfur Proteins; D010088:Oxidoreductases; C424907:quinol fumarate reductase; C040077:cytochrome bd terminal oxidase complex, E coli