Deaton JC, Solomon EI, Watt GD, Wetherbee PJ, Durfor CN. Electron paramagnetic resonance studies of the tungsten-containing formate dehydrogenase from Clostridium thermoaceticum.
Biochem Biophys Res Commun 1987;
149:424-30. [PMID:
2827642 DOI:
10.1016/0006-291x(87)90384-6]
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Abstract
The redox centers in the tungsten-containing formate dehydrogenase from Clostridium thermoaceticum were examined by potentiometric titration and electron paramagnetic resonance spectroscopy. At low temperature two overlapping iron-sulfur signals which correlated with enzymatic activity were observed with formal potentials near -400 mV vs. SHE. Based on their temperature dependences, one signal is assigned to a reduced Fe2S2 cluster and one to a reduced Fe4S4 cluster. Quantitation of signal intensity suggests two Fe2S2 and two Fe4S4 clusters per formate dehydrogenase molecule. Another signal (g = 2.101, 1.980, 1.950) present in low concentrations at more negative potentials was observable up to 200 degrees K and is not attributed to any iron-sulfur cluster. The possible origin of this signal is analyzed using ligand field theory, and the redox behavior is considered with respect to possible ligation at the active site.
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