Electron transfer after flash photolysis of mixed-valence carboxycytochrome c oxidase

Boelens, Rolf; Wever, Ron; Gelder, B.F. Van

doi:10.1016/0005-2728(82)90107-4

Cited by 72 publications

(47 citation statements)

References 28 publications

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“…This is about 0.1 V anaerobically [27] but increases to 0.6 V in the presence of 02 [28] (table 1). It has been possible to measure the rate of oxidation of CUA and cytochrome a directly in flash-photolysis experiments with the CO compounds of the mixedvalence state [27,29] and fully reduced oxidase [30,31]. Surprisingly the rate constants are very close to each other in both cycles (table 1).…”

Section: Kinetic Tests Of a Reaction Cyclementioning

confidence: 96%

“…an enzyme form in which cytochrome a and CUA are both oxidised, whereas the cytochrome a3-c~~ site is stabilized in the reduced state by CO binding. When the CO is photodissociated with a laser flash, there is a small back-flow of electrons from cytochrome a3-CUB to CuA [27,29]. From the measured relaxation time and equilibrium constant, the rate for electron transfer in the normal direction from Cua to the binuclear site was calculated to be 1.4 x lo4 s-l.…”

Section: A3-cubmentioning

confidence: 99%

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The mechanism of proton translocation in respiration and photosynthesis

Malmström

1989

FEBS Letters

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Redox-linked proton pump; Electron gating; Reorganization energy; Intrinsic uncoupling THE KEY PROCESSES OF BIOENERGETICSLife is a chemical phenomenon and, as such, much more complex and sophisticated than any man-made chemical system. Through milliards (American English, billions) of years of biological evolution, natural selection has led to elegant chemical solutions to the survival problems of living organisms on Earth. Superb examples of this are the key processes of bioenergetics, respiration and photosynthesis.Aerobic organisms derive most of the free energy necessary for life processes, such as growth, transport or locomotion, from the combustion of carbohydrates and fats with the dioxygen of air, leading to the formation of CO2 and H20. This could, however, not go on indefinitely, were it not for the fact that green plants in photosynthesis use the energy of the sun to resynthesize carbohydrate from CO2 and Hz0 with (fig. l), and this represents an ideal energy system which Man should try to imitate for his survival.Unraveling the secrets of photosynthesis and respiration is consequently an urgent challenge to the biochemist, but also an extremely demanding one. It is stated in a famous textbook of molecular biology [l] that "how light quanta are collected by the photosynthetic apparatus, or how a membrane protein pumps ions, increasingly have become the important biochemical questions that only chemically oriented scientists (as opposed to

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Section: Kinetic Tests Of a Reaction Cyclementioning

confidence: 96%

Section: A3-cubmentioning

confidence: 99%

The mechanism of proton translocation in respiration and photosynthesis

Malmström

1989

FEBS Letters

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“…Ͼ10 Ϫ5 s), photo-induced electron transfer can thus take place. These features have been exploited to investigate intraprotein electron transfer from photodissociated 5-coordinated heme a 3 in the active site of native cytochrome c oxidase, where CO acts as an inhibitor (2), and recently used to determine a rate as high as ϳ10 9 s Ϫ1 (3).…”

mentioning

confidence: 99%

“…1 Supported by the Biotechnology and Biological Sciences Research Council (UK) and the European Science Foundation. 2 Recipient of an EMBO long term fellowship. Present address: Institut de Biologie Physico-Chimique, UMR7141 CNRS/University Paris VI, 13 Rue Pierre et Marie Curie, 75005 Paris, France.…”

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confidence: 99%

Ligand Dynamics in an Electron Transfer Protein

Silkstone

Jasaitis

Wilson

et al. 2007

Journal of Biological Chemistry

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Substitution of the heme coordination residue Met-80 of the electron transport protein yeast iso-1-cytochrome c allows external ligands like CO to bind and thus increase the effective redox potential. This mutation, in principle, turns the protein into a quasi-native photoactivable electron donor. We have studied the kinetic and spectral characteristics of geminate recombination of heme and CO in a series of single M80X (X ‫؍‬ Ala, Ser, Asp, Arg) mutants, using femtosecond transient absorption spectroscopy. In these proteins, all geminate recombination occurs on the picosecond and early nanosecond time scale, in a multiphasic manner, in which heme relaxation takes place on the same time scale. The extent of geminate recombination varies from >99% (Ala, Ser) to ϳ70% (Arg), the latter value being in principle low enough for electron injection studies. The rates and extent of the CO geminate recombination phases are much higher than in functional ligand-binding proteins like myoglobin, presumably reflecting the rigid and hydrophobic properties of the heme environment, which are optimized for electron transfer. Thus, the dynamics of CO recombination in cytochrome c are a tool for studying the heme pocket, in a similar way as NO in myoglobin. We discuss the differences in the CO kinetics between the mutants in terms of the properties of the heme environment and strategies to enhance the CO escape yield. Experiments on double mutants in which Phe-82 is replaced by Asp or Gly as well as the M80D substitution indicate that such steric changes substantially increase the motional freedom-dissociated CO.

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“…In this work, we have studied proton uptake and release in the binuclear center following laser-flash photolysis of the carbon monoxide-mixed valence (partly reduced) complex of cytochrome c oxidase in the absence of dioxygen. This technique has previously been used to investigate internal electron-transfer reactions (14)(15)(16)(17)(18) and makes it also possible to study protonation reactions that are directly coupled to the electron transfers without interference from proton uptake associated with the reduction of dioxygen to water.…”

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confidence: 99%

Kinetic coupling between electron and proton transfer in cytochrome c oxidase: simultaneous measurements of conductance and absorbance changes.

Ädelroth

Sigurdson²,

Hallén³

et al. 1996

Proc. Natl. Acad. Sci. U.S.A.

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Bovine heart cytochrome c oxidase is an electron-current driven proton pump. To investigate the mechanism by which this pump operates it is important to study individual electron-and proton-transfer reactions in the enzyme, and key reactions in which they are kinetically and thermodynamically coupled. In this work, we have simultaneously measured absorbance changes associated with electron-transfer reactions and conductance changes associated with protonation reactions following pulsed illumination of the photolabile complex of partly reduced bovine cytochrome c oxidase and carbon monoxide. Following CO dissociation, several kinetic phases in the absorbance changes were observed with time constants ranging from -3 ,us to several milliseconds, reflecting internal electrontransfer reactions within the enzyme. The data show that the rate of one of these electron-transfer reactions, from cytochrome a3 to a on a millisecond time scale, is controlled by a proton-transfer reaction. These results are discussed in terms of a model in which cytochrome a3 interacts electrostatically with a protonatable group, L, in the vicinity of the binuclear center, in equilibrium with the bulk through a proton-conducting pathway, which determines the rate of proton transfer (and indirectly also of electron transfer). The interaction energy of cytochrome a3 with L was determined independently from the pH dependence of the extent of the millisecond-electron transfer and the number of protons released, as determined from the conductance measurements. The magnitude of the interaction energy, 70 meV (1 eV =

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Electron transfer after flash photolysis of mixed-valence carboxycytochrome c oxidase

Cited by 72 publications

References 28 publications

The mechanism of proton translocation in respiration and photosynthesis

The mechanism of proton translocation in respiration and photosynthesis

Ligand Dynamics in an Electron Transfer Protein

Kinetic coupling between electron and proton transfer in cytochrome c oxidase: simultaneous measurements of conductance and absorbance changes.

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