Spectroscopic characterization of the tungsten and iron centers in aldehyde ferredoxin oxidoreductases from two hyperthermophilic Archaea
- Univ. of Georgia, Athens, GA (United States)
The electronic and redox properties of iron and tungsten centers in the aldehyde ferredoxin oxidoreductases (AORs) from Pyrococcus furiosus (Pf) and pyrococcus strain ES-4 (ES-4) have been investigated by the combination of EPR and variable-temperature magnetic circular dichroism (VTMCD) spectroscopies. Parallel- and perpendicular-mode EPR studies of ES-4 AOR reveal a redox inactive `g = 16` resonance from an integer spin paramagnet. Seven distinct W(V) EPR signals have been observed during dye-mediated redox titrations of Pf AOR, and the four major W(V) species have been rigorously identified and characterized via EPR spectral simulations of natural abundances and {sup 183}W-enriched samples ({sup 183}W, I = 1/2, 14.28% natural abundance). Structures are proposed for each of the major W(V) species on the basis of EPR g values and {sup 183}W A values as compared to other biological and synthetic W(V)/Mo(V) centers, VTMCD spectra, and the available X-ray crystallographic and XAS data for Pf AOR and the Mo-containing DMSO redictase from Rhodobacter sphaeroides. Comparison with the limited spectroscopic data that are available for all known tungstoenzymes suggests two major classes of enzyme with distinct active site structures. 58 refs., 11 figs., 2 tabs.
- DOE Contract Number:
- FG09-88ER13901
- OSTI ID:
- 447214
- Journal Information:
- Journal of the American Chemical Society, Vol. 118, Issue 49; Other Information: PBD: 11 Dec 1996
- Country of Publication:
- United States
- Language:
- English
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