Iron complexes sulfur proteins

Figure 12-6. Iron-sulfur-protein complex (Fe4S4). d acid-labile sulfur Pr,apoprotein Cys, cysteine residue. Some iron-sulfur proteins contain two iron atoms and two sulfur atoms (FejSj).

Transport of reducing equivalents from NADH to FMN and structure of the iron-sulfur protein complex that mediates electron transport from FMNH2 to CoQ. Both FMN and the iron-sulfur centers are components of NADH-CoQ... 

The succinate dehydrogenase complex (complex II) consists primarily of the citric acid cycle enzyme succinate dehydrogenase and two iron-sulfur proteins. Complex II mediates the transfer of electrons from succinate to UQ. The... 

Figure 1 shows the complex ESR spectra from isolated cardiac mitochondria. They appear as a superposition of spectra from various paramagnetic components of the mitochondrial ETC. They are mainly iron-sulfur centers, denoted as Nl, N2, N3 - - 4 (located in complex I, NADFi-ubiquinone oxidoreductase), SI (complex II, succinate-ubiquinone oxidoreductase), and the Rieske iron-sulfur protein (complex III, ubihydroquinone-cytochrome C oxidoreductase). The positions of the components... 

Kimura, T., Nakamura, S., Huang, J.J., Chu, J-W, Wang, H-P, Tsernog-lou, D. Electron transport system for adrenocortical mitochondrial steroid hydroxylation reactions The mechanism of the hydroxylation reactions and properties of the flavoprotein-iron-sulfur protein complex. Ann. N. Y. Acad. Sci. 212, 94-106 (1973)... 

Three protein complexes have been isolated, including the flavoprotein (FP), iron-sulfur protein (IP), and hydrophobic protein (HP). FP contains three peptides (of mass 51, 24, and 10 kD) and bound FMN and has 2 Fe-S centers (a 2Fe-2S center and a 4Fe-4S center). IP contains six peptides and at least 3 Fe-S centers. HP contains at least seven peptides and one Fe-S center. 

In 1964, Rieske and co-workers reported the observation of an EPR signal around g = 1.90 in the cytochrome bci complex (1). They succeeded in the isolation of the iron sulfur protein that gave rise to the EPR signal and showed that it contained a [2Fe-2S] cluster. Over the... 

Rieske proteins are constituents of the be complexes that are hydro-quinone-oxidizing multisubunit membrane proteins. All be complexes, that is, bci complexes in mitochondria and bacteria, b f complexes in chloroplasts, and corresponding complexes in menaquinone-oxidizing bacteria, contain three subunits cytochrome b (cytochrome 6e in b f complexes), cytochrome Ci (cytochrome f in b(,f complexes), and the Rieske iron sulfur protein. Cytochrome 6 is a membrane protein, whereas the Rieske protein, cytochrome Ci, and cytochrome f consist of water-soluble catalytic domains that are bound to cytochrome b through a membrane anchor. In Rieske proteins, the membrane anchor can be identified as an N-terminal hydrophobic sequence (13). 

Resonance Raman (RR) spectroscopy provides information about the vibrational characteristics of a chromophore, for example, a metal center, within the complex environment of a protein. In RR spectra, those vibrational transitions are observed selectively that are coupled to electronic transitions. In iron sulfur proteins, this technique has been used to resolve the complex electronic absorption spectra and to identify both vibrational and electronic transitions. 

SIMPLE AND COMPLEX IRON-SULFUR PROTEINS IN SULFATE REDUCING BACTERIA... 

In particular, the study of SRB ferredoxins enables us to survey the different properties of simple iron-sulfur proteins, including electron transfer, flexibility in coordination chemistry, and ability to undergo cluster interconversions. Most of the observations can be extrapolated to more complex situations. 

The many redox reactions that take place within a cell make use of metalloproteins with a wide range of electron transfer potentials. To name just a few of their functions, these proteins play key roles in respiration, photosynthesis, and nitrogen fixation. Some of them simply shuttle electrons to or from enzymes that require electron transfer as part of their catalytic activity. In many other cases, a complex enzyme may incorporate its own electron transfer centers. There are three general categories of transition metal redox centers cytochromes, blue copper proteins, and iron-sulfur proteins. 

The cyt b6f complex (/ stands for feuille, the French word for "leaf") consists of four subunits—one molecule of cyt/, one heme-containing cyt b6, one iron-sulfur protein, and one bound plastoquinol. The cyt b6f complex transports electrons from the outside to the inside of the thylakoid membrane. 

Simple and Complex Iron-Sulfur Proteins in Sulfate Reducing Bacteria... 

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