Activation by reduction of the resting form of cytochrome c oxidase: Tests of different models and evidence for the involvement of CuB

Wrigglesworth, John M.; Elsden, Jennifer; Chapman, A. Chaston; Water, Neil Van der; Grahn, Michael F.

doi:10.1016/0005-2728(88)90023-0

Cited by 35 publications

(22 citation statements)

References 42 publications

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“…The results presented in the present paper appear to support earlier findings of Nicholls and Hildebrandt (1978) and newer findings of Wrigglesworth et al (1988) which indicate the existence of a low spin-activated form of cytochrome a3. This form of the enzyme reported here, using a purified preparation, was also seen in intact mitochondria during potentiometric titrations ).…”

Section: Introductionsupporting

confidence: 91%

Characterization of two low Em forms of cytochrome a3 and their carbon monoxide complexes in mammalian cytochrome c oxidase

Sidhu

Hendler

1990

Biophysical Journal

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Evidence is presented for the existence of two forms of low-potential cytochrome a3. One appears to be similar to the low-spin form reported by Nicholls, P., and V. Hildebrandt (1978 Biochem. J. 173:65-72) and Wrigglesworth, J. M., J. Elsden, A. Chapman, N. Van der Water, and M. F. Grahn (1988. Biochim. Biophys. Acta. 936:452-464). It has a reduced Soret peak near 428 nm and a prominent alpha peak near 602 nm. This form is seen when the enzyme is either supplemented with lipoprotein or incorporated into a liposomal membrane, preexposed to a voltage greater than 400 mV for at least 30 min, and titrated in the presence of approximately 1 mM K3Fe(CN)6. The other form has a reduced Soret peak near 446 nm, and no prominent alpha peak. The 428-nm form has an Em near 175 mV and forms a CO complex with an Em near 225 mV. The 446-nm form has an Em near 200 mV and forms a CO complex with an Em near 335 mV.

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Section: Introductionsupporting

confidence: 91%

Characterization of two low Em forms of cytochrome a3 and their carbon monoxide complexes in mammalian cytochrome c oxidase

Sidhu

Hendler

1990

Biophysical Journal

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“…oxidase that has just completed a reaction cycle and is in the state we define as O H ; pre-primed to pump protons. There are likely a large number of oxidized oxidase states, given the number of protons sites that may or may not be occupied, but only one is fully catalytically competent (Brand et al 2007; Belevich and Verkhovsky 2008; Jancura et al 2006; Wrigglesworth et al 1988; Brunori et al 1981, 1979; Antonini et al 1977). This state is defined by Wikstrom as O~ or O H (Wikstrom 2004; Verkhovsky et al 1999; Bloch et al 2004).…”

Section: The Modelmentioning

confidence: 99%

A chemically explicit model for the mechanism of proton pumping in heme–copper oxidases

Sharpe

Ferguson‐Miller

2008

J Bioenerg Biomembr

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A mechanism for proton pumping is described that is based on chemiosmotic principles and the detailed molecular structures now available for cytochrome oxidases. The importance of conserved water positions and a step-wise gated process of proton translocation is emphasized, where discrete electron transfer events are coupled to proton uptake and expulsion. The trajectory of each pumped proton is the same for all four substrate electrons. An essential role for the His-Tyr cross-linked species is discussed, in gating of the D-and K-channels and as an acceptor/donor of electrons and protons at the binuclear center.

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“…This reaction scheme with its two states for oxidized enzyme does not take into account that there are altogether six forms of oxidized oxidase described in the literature: "resting" (15, 16), "slow" (17)(18)(19)(20)(21), "pulsed" (15,16), O (12,14), O H (12,14), and "fast" form (18,20). The term resting is used for oxidase that shows low catalytic activity because of slow internal ET from Cu A -heme a to the catalytic site (15,16).…”

mentioning

confidence: 99%

Spectral and Kinetic Equivalence of Oxidized Cytochrome c Oxidase as Isolated and “Activated” by Reoxidation

Jancura

Berka

Antalı́k

et al. 2006

Journal of Biological Chemistry

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The spectral and kinetic characteristics of two oxidized states of bovine heart cytochrome c oxidase (CcO) have been compared. The first is the oxidized state of enzyme isolated in the fast form (O) and the second is the form that is obtained immediately after oxidation of fully reduced CcO with O 2 (O H ). No observable differences were found between O and O H states in: (i) the rate of anaerobic reduction of heme a 3 for both the detergent-solubilized enzyme and for enzyme embedded in its natural membraneous environment, (ii) the one-electron distribution between heme a 3 and Cu B in the course of the full anaerobic reduction, (iii) the optical and (iv) EPR spectra. Within experimental error of these characteristics both forms are identical. Based on these observations it is concluded that the reduction potentials and the ligation states of heme a 3 and Cu B are the same for CcO in the O and O H states.Mitochondrial cytochrome c oxidase (CcO) 2 transfers electrons from cytochrome c to dioxygen. The reduction of O 2 to water is associated with the generation of a transmembrane proton gradient. Two processes contribute to the development of this gradient. The first is the oxidation of ferrocytochrome c from the cytosolic side of the inner mitochondrial membrane coupled to proton consumption for water formation from the matrix compartment of mitochondria. The second process is proton pumping during which protons are translocated from the matrix space to the cytosolic side of the membrane (1).In CcO four redox centers participate in electron transfer (ET) and reduction of O 2 to H 2 O. Three of these centers, heme a, heme a 3 , and copper ion, called Cu B , are in subunit I and a dinuclear copper center Cu A , is located in subunit II (2). Cu A serves as the acceptor of electrons either from ferrocytochrome c or from artificial electron donors (3-7). Electrons received by the oxidase are rapidly distributed between Cu A and heme a on the microsecond time scale (4, 5, 7-10). ET continues further to the catalytic center composed of heme a 3 and Cu B where O 2 is reduced to water.The part of the catalytic cycle during which electrons are delivered to CcO, prior to reaction with O 2 , is usually referred to as the reductive phase. In the subsequent oxidative phase the reduced enzyme reacts with O 2 . It was proposed (11) and demonstrated later that proton pumping takes place in both the reductive and oxidative phases (12)(13)(14). Two protons are pumped in the oxidative phase when fully reduced CcO is oxidized by oxygen (12,14). Subsequently, if this freshly oxidized enzyme is reduced by two electrons two additional protons are translocated across the membrane (12, 14).However, proton translocation in the reductive phase is only observed with freshly oxidized enzyme. This reoxidized enzyme appears to be in a metastable state, which relaxes relatively slowly in the absence of electron donors to the stable oxidized form on a time scale of seconds. These two forms of oxidized enzyme, CcO as it exists immediately after ox...

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Activation by reduction of the resting form of cytochrome c oxidase: Tests of different models and evidence for the involvement of CuB

Cited by 35 publications

References 42 publications

Characterization of two low Em forms of cytochrome a3 and their carbon monoxide complexes in mammalian cytochrome c oxidase

Characterization of two low Em forms of cytochrome a3 and their carbon monoxide complexes in mammalian cytochrome c oxidase

A chemically explicit model for the mechanism of proton pumping in heme–copper oxidases

Spectral and Kinetic Equivalence of Oxidized Cytochrome c Oxidase as Isolated and “Activated” by Reoxidation

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