Iron-sulfur proteins characterization

For all known cases of iron-sulfur proteins, J > 0, meaning that the system is antiferromagnetically coupled through the Fe-S-Fe moiety. Equation (4) produces a series of levels, each characterized by a total spin S, with an associated energy, which are populated according to the Boltzmann distribution. Note that for each S level there is in principle an electron relaxation time. For most purposes it is convenient to refer to an effective relaxation time for the whole cluster. 

Corrinoid iron-sulfur protein (CFeSP) purified and characterized acetyl-CoA synthesis reconstituted from CH3-H4 folate, CO, and CoA using purified proteins. ... 

A preliminaiy characterization of a new iron—sulfur protein isolated from Desulfovibrio vulgaris Hildenborough was reported in 1989 124). The protein contained approximately 6 iron and 6 inorganic sulfur atoms per molecule. The FPR spectrum of the dithionite reduced protein exhibited an S = signal similar to what was found for synthetic compounds with a [6Fe-6S] core (prismane core). No other FPR signals were reported at this time, and based on the observed similarity it was suggested that this peculiar iron-sulfur protein contained a [6Fe-6S] cluster. Because it had no known function, the pro-... 

Rosner BM, B Schink (1995) Purification and characterization of acetylene hydratase of Pelobacter acetyle-nicus, a tungsten iron-sulfur protein. J Bacterial 177 5767-5772. 

Maillard J, W Schumacher, F Vazquez, C Regeard, WR Hagen, C Holliger (2003) Characterization of the corrinoid iron-sulfur protein tetrachloroethene reductive dehalogenase of Dehalobacter restrictus. Appl Environ Microbiol 69 4628-4638. 

Pereira MM, Carita JN, Teixeira M. 1999. Membrane-bound electron transfer chain of the ther-mohalophilic bacterium Rhodothermus marinus Characterization of the iron- sulfur centers from the dehydrogenases and investigation of the high-potential iron- sulfur protein function by in vitro reconstitution of the respiratory chain. Biochemistry 38 1276. 

Although heme is absent in Clostridia, it was early recognized that anaerobic bacteria may contain substantial levels of iron (44). To date the best characterized iron compounds from this source are the iron-sulfur proteins termed ferredoxins and rubredoxins. Molecular structures of representatives of both types of protein have been worked out by Jensen and his colleagues by X-ray diffraction analysis (see below). 

There is some evidence that the iron-sulfur protein, FhuF, participates in the mobilization of iron from hydroxamate siderophores in E. coli (Muller et ah, 1998 Hantke, K. unpublished observations). However, a reductase activity of FhuF has not been demonstrated. Many siderophore-iron reductases have been shown to be active in vitro and some have been purified. The characterization of these reductases has revealed them to be flavin reductases which obtain the electrons for flavin reduction from NAD(P)H, and whose main functions are in areas other than reduction of ferric iron (e.g. flavin reductase Fre, sulfite reductase). To date, no specialized siderophore-iron reductases have been identified. It has been suggested that the reduced flavins from flavin oxidoreductases are the electron donors for ferric iron reduction (Fontecave et ah, 1994). Recently it has been shown, after a fruitless search for a reducing enzyme, that reduction of Co3+ in cobalamin is achieved by reduced flavin. Also in this case it was suggested that cobalamins and corrinoids are reduced in vivo by flavins which may be generated by the flavin... 

Fe-S proteins contain four basic core structures, which have been characterized crystal-lographically both in model compounds (Rao and Holm, 2004) and in iron-sulfur proteins. These are (Figure 3.6), respectively, (A) rubredoxins found only in bacteria, in which the [Fe-S] cluster consists of a single Fe atom liganded to four Cys residues—the iron atom... 

Lesniak J, Barton WA, Nikolov DB (2002) Structural and functional characterization of the Pseudomonas hydroperoxide resistance protein Ohr. EMBO J 21 6649-6659 Lesniak J, Barton WA, Nikolov DB (2003) Structural and functional features of the Escherichia coli hydroperoxide resistance protein OsmC. Protein Sci 12 2838-2843 Lill R, Kispal G (2000) Maturation of cellular Fe-S proteins an essential function of mitochondria. Trends Biochem Sci 25 352-356 Lill R, Miihlenhoff U (2005) Iron-sulfur protein biogenesis in eukaryotes. Trends Biochem Sci 30 133-141... 

The components of the electron-transfer chain in mitochondria are shown in Figure 69. The sites at which ATP is synthesized are noted. The cytochromes may be characterized by UV-vis studies on membranes, usually by difference spectra. The iron-sulfur proteins may be identified by ESR spectroscopy, but MCD may be of particular value in characterizing isolated clusters. 

Interesting results have been obtained for mitochondrial particles prepared from the yeast Candida utilis grown in a medium containing 57Fe. This allowed hyperfine interactions for 57Fe atoms in the ESR spectrum to be characterized. Certain of the iron-sulfur proteins are also proton pumps. 

The molar masses of the 2-oxoacid ferredoxin oxidoreductases are 200,000-300,000 g/mol and they are composed of four subunits of the kind a2p2. It has been shown that halobacteria have only these systems of 2-oxoacid ferredoxin oxidoreductases. The two enzymes of H. halobium (pyruvate and oxoglutarate) were isolated and characterized by Kerscher and Oesterhelt (1981a). These systems proved to be thiamin diphosphate-containing iron-sulfur proteins. The relative stability of the halobacterial enzymes enabled detailed analysis of the various steps of the catalytic cycles (Kerscher and Oesterhelt, 1981b), demonstrating two distinct steps of one-electron transfer reactions. 

Lillig, C.H., Bemdt, C., Vergnolle, O., Lonn, M.E., Hudemann, C., Bill, E., and Holmgren, A. 2005. Characterization of human glutaredoxin 2 as iron-sulfur protein a possible role as redox sensor. Proc. Natl. Acad. Sci. USA 10 8168-8173. 

Link, T. A., Saynovits, M., Assmann, C., Iwata, S., Ohnishi, T., and von Jagow, G., 1996. Isolation, characterization, and crystallization of a water-soluble fragment of the Rieske iron-sulfur protein of bovine heart mitochondrial bcl complex, Eur. J. Biochem. 237 71n75. 

E. M. Maes, "Structural Characterization of Iron and Copper Active Sites by Resonance Raman Spectroscopy Nitrophorin, Nitrite Reductase, and Iron-Sulfur Proteins, PhD. Dissertation, University of Houston, 2000. 

This review is a survey of the research on the direct electron transfer (DET) between biomolecules and electrodes for the development of reagentless biosensors. Both the catalytic reaction of a protein or an enzyme and the coupling with further reaction have been used analytically. For better understanding and a better overview, this chapter begins with a description of electron transfer processes of redox proteins at electrodes. Then the behaviour of the relevant proteins and enzymes at electrodes is briefly characterized and the respective biosensors are described. In the last section sensors for superoxide, nitric oxide and peroxide are presented. These have been developed with several proteins and enzymes. The review is far from complete, for example, the large class of iron-sulfur proteins has hardly been touched. Here the interested reader may consult recent reviews and work cited therein [1,19]. 

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