Pyrococcus furiosus reductase

The molyhdopterin cofactor, as found in different enzymes, may be present either as the nucleoside monophosphate or in the dinucleotide form. In some cases the molybdenum atom binds one single cofactor molecule, while in others, two pterin cofactors coordinate the metal. Molyhdopterin cytosine dinucleotide (MCD) is found in AORs from sulfate reducers, and molyhdopterin adenine dinucleotide and molyb-dopterin hypoxanthine dinucleotide were reported for other enzymes (205). The first structural evidence for binding of the dithiolene group of the pterin tricyclic system to molybdenum was shown for the AOR from Pyrococcus furiosus and D. gigas (199). In the latter, one molyb-dopterin cytosine dinucleotide (MCD) is used for molybdenum ligation. Two molecules of MGD are present in the formate dehydrogenase and nitrate reductase. 

Ferredoxin rednctases in Pyrococcus furiosus inclnding aldehyde ferredoxin reductase, glyceraldehyde-3-phosphate ferredoxin oxidorednctase, and formaldehyde ferredoxin reductase (Roy et al. 1999). 

The ability to catalyse the evolution or oxidation of H2 may have been exploited by the earliest life forms as H2 would have been present in the early prebiotic environments. The origins of the proton-dependent chemiosmotic mechanism for ATP synthesis may also reflect the formation of proton gradients created by hydrogenases on either side of the cytoplasmic membrane. In addition, it has been speculated that the coupling of H2 and S metabolisms was also of fundamental importance in the origin of life. These two processes seem intimately coupled in the bifunctional sulfhydrogenase found in Pyrococcus furiosus (a combination of subunits for hydrogenase and sulfite reductase) which can dispose of excess reductant either by the reduction of protons to H2 or S° to H2S (Ma et al. 1993 Pedroni et al. 1995). 

Ma, K., Schicho, R. N., Kelly, R. M. and Adams, M. W. W. (1993) Hydrogenase of the hyper-thermophile Pyrococcus furiosus is an elemental sulfur reductase or sulfhydrogenase Evidence for a sulfur-reducing hydrogenase ancestor. Proc. Natl. Acad. Sci. USA, 90, 5341-4. 

Pedroni, P., Della Volpe, A., Galli, G., Mura, G. M., Pratesi, C. and Grandi, G. (1995) Characterization of the locus encoding the [Ni-Fe] sulfhydrogenase from the archaeon Pyrococcus furiosus Evidence for a relationship to bacterial sulfite reductases. Microbiology, 141, 449-58. 

Some aspects of the proposed Rbr/Rbo oxidative stress defense system in D. vulgaris resemble those recently suggested for oxidative stress protection in the anaerobic hyperthermophilic archaeon Pyrococcus furiosus (Jenney et al. 1999). Pyrococcus furiosus contains an Nlr-like protein with superoxide reductase activity as well as an Rbr, the genes for which are tandemly located. The microorganismic segregation of SOD/catalase between aerobes and anaerobes appears to be less distinct than for Rbo/Rbr, which, as noted above, have so far been found only in air-sensitive microbes (Kirschvink et al. 2000). The latter segregation suggests that the Rbo/Rbr oxidative stress protection system is well suited to protection of anaerobic life in an aerobic world. 

The aldehyde ferredoxin oxidoreductase from the hyperthermophile Pyrococcus furiosus was the first molybdopterin-dependent enzyme for which a three-dimensional structure became available.683,684 The tungstoenzyme resembles that of the related molybdo-enzyme (Fig. 16-31). A similar ferredoxin-dependent enzyme reduces glyceraldehyde-3-phosphate.685 Another member of the tungstoenzyme aldehyde oxidoreductase family is carboxylic acid reductase, an enzyme found in certain acetogenic clostridia. It is able to use reduced ferredoxin to convert unactivated carboxylic acids into aldehydes, even though E° for the acetaldehyde/acetate couple is -0.58 V.686... 

Robust voltammetry and in situ STM to molecular resolution have been achieved when the Au(lll)-electrode surfaces are modified by linker molecules, Fig. 8-10, prior to protein adsorption. Comprehensive voltammetric data are available for horse heart cyt and P. aeruginosa The latter protein, which we address in the next Section, has in a sense emerged as a paradigm for nanoscale bioelectrochemistry. We address first briefly two other proteins, viz. the electron transfer iron-sulfur protein Pyrococcus furiosus ferredoxin and the redox metalloenz5mie Achromobacter xylosoxidans copper nitrite reductase. 

Spectroscopic studies of Pyrococcus furiosus superoxide reductase Implications for active-site structures and the catalytic mechanism. J. Am. Chem. Soc. 124, 788-805. 

Two accidentally similar EPR spectra provide a focus for discussion of assigning transitions in high-spin, non-heme ferric proteins. Several superoxide reductase (SOR) enzymes have been characterized recently [7]. The SOR from Pyrococcus furiosus has an EPR spectrum, shown in Figure 1 [8], superficially resembling that... 

Figure 1. EPR spectra of ferric iron in superoxide reductase (SOR) of Pyrococcus furiosus. X-band EPR spectra, at low temperature (as indicated on the figure), of recombinant SOR (0.5 mM) in 50 mM HEPES, pH 7.5, are showtL The ratio of intensities at g = 5.8 (middle Kramers doublet) and g = 7.3 (lower Kramers doublet) is shown in the upper panel. The figure is fiorn Fig. 2 of Clay et aL [8], with permission of the pubUsher.

Yeh AP, Hu YL, Jenney FE, Adams MWW, Rees DC. 2000. Structures of the superoxide reductase from Pyrococcus furiosus in the oxidized and reduced states. Biochemistry 39(10) 2499-2508. 

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