Cytochrome C, electron

Gray HB, Winkler JR (1996) Electron transfer in proteins. Annu Rev Biochem 65 537 Fedurco M (2000) Redox reactions of heme-containing metalloproteins dynamic effects of self-assembled monolayers on thermodynamics and kinetics of cytochrome c electron-transfer reactions. Coord Chem Rev 209 263... 

Approximately 2.5 molecules of ADP can be phosphorylated to ATP for each pair of electrons that traverse the electron-transport chain from NADH to 02. About 1.5 molecules of ATP are formed for a pair of electrons that enter the chain via succinate dehydrogenase or other flavoproteins such as glycerol-3-phosphate dehydrogenase. Approximately one molecule of ATP is formed for each pair of electrons that enters via cytochrome c. Electron flow through each of complexes I, III, and IV thus is coupled to phosphorylation. 

Coenzyme Q passes electrons through iron-sulfur complexes to cytochromes b and ch which transfer the electrons to cytochrome c. In the ferric Fe3+ state, the heme iron can accept one electron and be reduced to the ferrous state Fe2+. Since the cytochromes carry one electron at a time, two molecules on each cytochrome complex are reduced for every molecule of NADH that is oxidized. The electron transfer from coenzyme Q to cytochrome c produces energy, which pumps protons across the inner mitochondrial membrane. The proton gradient produces one ATP for every coenzyme Q-hydrogen that transfers two electrons to cytochrome c. Electrons from FADH2, produced by reactions such as the oxidation of succinate to fumarate, enter the electron transfer chain at the coenzyme Q level. 

FIGURE 3. The Catalytic Cycle for Flavocytochrome 62 F, flavin H, heme Cyt c, cytochrome c. Electrons are shown as hlack dots and are used to indicate the two-electron reduced flavin (hydroquinone), F with two dots one-electron reduced flavin (semiquinone), F with one dot reduced heme, H with one dot reduced cytochrome c, Cyt c with one dot. The rate constants shown are for S. cerevisiae flavocytochrome hi at 25 C, pH 7.5, I = O.IOM. The whole catalytic cycle turns over at approximately 100 s ". The details of the cycle are described in the main text. 

Two cytochromes have been studied so far. In case of the electron-transfer protein cytochrome c, electronic structure calculations helped clarify the intriguing nature of the Fe-S bond at the active site [40] whereas for cytochrome P450, steps of the enzymatic reaction were investigated [41-44]. The P450 family of enzymes is involved in the metabolism of endogenous and xenobiotic compounds and this work can therefore be of potential use in toxicology research. 

Concur, D. W., Hill, H. A. O., Moore, G. R., Whitford, D., Williams, R. J. P., The Modulation of Cytochrome C Electron Self-Exchange by Site-Specific Chemical Modification and Anion Binding , FEBS Utt. 206 (1986) 15-19. 

In presence of TNS, reduction of cytochrome c occurs in the range of minutes instead of seconds, as it is the case for the reduction with flavocytochrome b2 or isolated cytochrome b2 core. Thus, the relative distance and orientation of the FMN, TNS and heme planes induces an electron transfer pathway different from that known for the cytochrome b2 - cytochrome c electron transfer. This clearly shows the importance of cytochrome b2 core in the electron transfer to cytochrome c. 

A). The rapidity of cytochrome c electron transfer may partly be attriliuted to the lack of substantial nuclear motion upon redox (c/. Franck-Condon principle) together with the fast low-spin Fe " to low-spin Fe" reduction rate. 

Pappa, H. S. Tajbaksh, S. Saunders, A. J. Pielak, G. J. Poulos, T. L., Probing the cytochrome c peroxidase-cytochrome c electron transfer reaction using site specific cross-ttnking. Biochemistry 1996, 35,4837-4845. 

T.L. Poulos and J. Kraut, A hypothetical model of the cytochrome c peroxidase.cytochrome c electron transfer complex, J. Biol. Chem. 255 10322 (1980),... 

It is apparent that the cytochrome c electron transfer reaction at mercury electrodes is complex and dependent on a number of parameters. The adsorption of cytochrome c at mercury is in and of itself a complicated process. The formation of the first monolayer is rapid and chemically irreversible. 

In a recent report, it was demonstrated that adsorption of 4,4 -bipyridine on platinum led to quasi-reversible rates of electron transfer with cytochrome c as evidenced by cyclic voltammetry. However, the concentration of 4,4 -bipyridine required to produce this electrochemical response was five times that which is required at gold electrodes. This difference was ascribed to the difference in the tendency of 4,4 -bipyridine to adsorb at gold and platinum electrodes. These results indicate that the use of 4,4 -bipyridine may be applicable to other solid electrodes as well for the study of cytochrome c electron transfer reactions. 

Cytochrome c Electron transport Hemin primary valence bond to the protein +... 

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