Oxidation-reduction ptoentials of cytochromes in mitochondria

Pl, Dutton; Df, Wilson; Cp, Lee

doi:10.1021/bi00828a006

Cited by 344 publications

(113 citation statements)

References 20 publications

(9 reference statements)

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“…Such downward shifts can be ascribed to the negatively charged surface on which the protein is adsorbed. The sign and extend of the shift agree well with E m shifts for cyt c bound to mitochondrial membranes 35,36 and to photosynthetic reaction centers. 37 Figure 2D shows a cyclic voltammogram obtained for the cyt b maquette adsorbed on MUA/Au electrodes.…”

Section: Cyclic Voltammetry Of Heme Proteins On Mua/gold Insupporting

confidence: 66%

De Novo Design of a CytochromebMaquette for Electron Transfer and Coupled Reactions on Electrodes

et al. 2001

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Experimental explorations of functional mechanisms in natural electron-transfer proteins are often frustrated by their fragility and extreme complexity. We have designed and synthesized four-R-helix-bundle redox proteins, maquettes, that are much simplified and more robust than natural redox proteins and can be designed to bind onto electrode surfaces to facilitate systematic investigations. The points of interest that can be now assessed are not only the processes that govern biological assembly of equilibrium structures, electrochemistry, and electron tunneling rates but also how these factors are coupled together to effect redox driven catalysis. Here we describe maquettes that bis-histidine ligate protoporphyrin IX (heme), much like native b cytochromes, as well as contain charged surface patches, much like native cytochrome c. The positively charged residues aid adsorption to negatively charged surfaces, such as gold electrodes modified by 11-mercaptoundecanoic acid, and facilitate cyclic voltammetry (CV) measurements. CV demonstrates the reversible electrochemistry typical for cytochrome b as well as the coupling of the b-heme oxidation and reduction to proton exchange. The pH dependency of redox midpoint potentials reveals a major (three pH units) shift of the pK a which matches the shift previously shown to originate in nearby glutamates 1 . The redox potentials correspondingly shift from -0.24 (pH > pK red , deprotonated) to -0.11 V (pH < pK ox , protonated). The rate of electron transfer at zero driving force between the hemes and the gold electrode was determined to be 120 s -1 , a rate consistent with tunneling through the mercaptoundecanoic acid spacer and suggesting that the coupled proton exchange is not rate limiting. Reduction of the heme in the presence of CO-saturated buffer shifted the oxidation peak from -0.2 to +0.35 V, indicating massive preferential CO binding to the reduced heme. Consistent with solution spectroscopy, CO must displace one axial histidine to the heme to form the His-CO form of the ferrous heme. The CO is released upon heme oxidation at high potentials. In contrast to coupled proton exchange, CO binding/release and ligand exchange are slow on the time scale of electron tunneling between the heme edge and the electrode.

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Section: Cyclic Voltammetry Of Heme Proteins On Mua/gold Insupporting

confidence: 66%

De Novo Design of a CytochromebMaquette for Electron Transfer and Coupled Reactions on Electrodes

et al. 2001

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“…It has been shown that redox potentials of ctype cytochromes can be influenced by binding with other materials, particularly membranes. For example, the solubilization of a membrane-bound cytochrome c from Azotobacter lowered its redox potential from 320 mV to 278 mV [6] and shifts in E,,, of mammalian cytochrome c from 280 mV to 230 mV when bound to various membranes have been shown [7]. Properties of haem groups in proteins may be influenced by the ligands to the iron and the environment provided by the folded polypeptide [8].…”

Section: Resultsmentioning

confidence: 99%

Redox potential of the cytochrome c in the flavocytochrome p‐cresol methylhydroxylase

Hopper

1983

FEBS Letters

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The redox potential of the cytochrome c in 5 flavocytochrome c proteins, all p-cresol methylhydroxylases purified from species of Pseudomonas, was measured. All gave similar values ranging from 226-250 mV. Two of the enzymes, from Pseudomonas putida NClB 9866 and NClB 9869, were resolved into their flavoprotein and cytochrome subunits and the redox potentials of the isolated cytochrome c subunits measured. The values for these were 60-70 mV below those for the whole enzymes but, in both cases, reconstitution of active enzyme by addition of the flavoprotein subunit restored the original potential. p-Cresol methylhydroxylaseFlavocytochrome

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“…+ 0.058V vs. Ag|AgCl (3M NaCl)) [30]. This shift was commonly observed when cyt c binds to membranes and other surface [19,[31][32][33][34]. …”

Section: Electrostatic Interactions Of T-cooh+t-nh 2 |Au With Cyt Cmentioning

confidence: 87%

Voltammetry of immobilized cytochrome c on novel binary self-assembled monolayers of thioctic acid and thioctic amide modified gold electrodes

Jin

et al. 2006

Journal of Electroanalytical Chemistry

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Horse heart cytochrome c (cyt c) was adsorbed on the binary self-assembled monolayers (SAMs) composed of thioctic acid (T-COOH) and thioctic amide (T-NH 2 ) at gold electrodes via electrostatic interaction. The cyt c adsorbed on the modified gold electrode exhibited well-defined reversible electrochemical behavior in 10 mM phosphate buffer solution (PBS, pH 7.0). The surface concentration (Г) of electroactive species, cyt c, on the binary SAMs was higher than that in single-component SAMs of T-COOH, and reached a maximum value of 9.2×10 -12 mol cm -2 when the ratio of T-COOH to T-NH 2 in adsorption solution was of 3:2, and the formal potential

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Oxidation-reduction ptoentials of cytochromes in mitochondria

Cited by 344 publications

References 20 publications

De Novo Design of a CytochromebMaquette for Electron Transfer and Coupled Reactions on Electrodes

De Novo Design of a CytochromebMaquette for Electron Transfer and Coupled Reactions on Electrodes

Redox potential of the cytochrome c in the flavocytochrome p‐cresol methylhydroxylase

Voltammetry of immobilized cytochrome c on novel binary self-assembled monolayers of thioctic acid and thioctic amide modified gold electrodes

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