Functions of the hydrophilic channels in protonmotive cytochrome
            <i>c</i>
            oxidase

Rich, Peter R.; Maréchal, Amandine

doi:10.1098/rsif.2013.0183

Cited by 93 publications

(86 citation statements)

References 136 publications

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“…Each electron transfer from Cu A to the O 2 reduction site is coupled with pumping of one proton equivalent. Thus, four protons are pumped to the P-side from the Mg/H 2 O cluster in a single catalytic cycle (1,2,17,18). After releasing two water molecules, the ligandfree Fe a3 2ϩ induces the channel open to provide the original state ( Fig.…”

Section: The Crucial Involvement Of the Mg/h 2 O Cluster In The Catalmentioning

confidence: 99%

The Mg2+-containing Water Cluster of Mammalian Cytochrome c Oxidase Collects Four Pumping Proton Equivalents in Each Catalytic Cycle

Yano¹,

Muramoto

Shimada³

et al. 2016

Journal of Biological Chemistry

132

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Bovine heart cytochrome c oxidase (CcO) pumps four proton equivalents per catalytic cycle through the H-pathway, a protonconducting pathway, which includes a hydrogen bond network and a water channel operating in tandem. Protons are transferred by H 3 O ؉ through the water channel from the N-side into the hydrogen bond network, where they are pumped to the P-side by electrostatic repulsion between protons and net positive charges created at heme a as a result of electron donation to O 2 bound to heme a 3 . To block backward proton movement, the water channel remains closed after O 2 binding until the sequential four-proton pumping process is complete. Thus, the hydrogen bond network must collect four proton equivalents before O 2 binding. However, a region with the capacity to accept four proton equivalents was not discernable in the x-ray structures of the hydrogen bond network. The present x-ray structures of oxidized/reduced bovine CcO are improved from 1.8/1.9 to 1.5/1.6 Å resolution, increasing the structural information by 1.7/1.6 times and revealing that a large water cluster, which includes a Mg 2؉ ion, is linked to the H-pathway. The cluster contains enough proton acceptor groups to retain four proton equivalents. The redox-coupled x-ray structural changes in Glu 198 , which bridges the Mg 2؉ and Cu A (the initial electron acceptor from cytochrome c) sites, suggest that the Cu A -Glu 198 -Mg 2؉ system drives redox-coupled transfer of protons pooled in the water cluster to the H-pathway. Thus, these x-ray structures indicate that the Mg 2؉ -containing water cluster is the crucial structural element providing the effective proton pumping in bovine CcO.Cytochrome c oxidase (CcO) 3 reduces molecular oxygen (O 2 ) in a reaction coupled with a proton pumping process. After binding of O 2 to the O 2 reduction site (which includes two redox-active metal sites, heme a 3 and Cu B ), four electron equivalents are sequentially donated from cytochrome c via two additional redox active metal sites, Cu A and heme a. Each of the four electron transfers is coupled to the pumping of a single proton equivalent (1, 2).High resolution x-ray structural studies together with mutational analyses for bovine CcO show a possible proton pumping pathway, known as the H-pathway, which includes a hydrogen bond network and a water channel functioning in tandem (1, 2). The water channel provides access of water molecules (or H 3 O ϩ ions) inside the mitochondrial inner membrane (the N-side) to one end of the hydrogen bond network that extends to the outside of the mitochondrial inner membrane (the P-side). The hydrogen bond network interacts tightly with heme a by forming two hydrogen bonds between the formyl group of heme a and Arg 38 in the hydrogen bond network and between the A-ring propionate of heme a and a fixed water molecule in the hydrogen bond network (1, 2). The net positive charge increase in heme a, which occurs upon electron donation from heme a to the O 2 reduction site to be delocalized to the formyl and propionate gro...

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Section: The Crucial Involvement Of the Mg/h 2 O Cluster In The Catalmentioning

confidence: 99%

The Mg2+-containing Water Cluster of Mammalian Cytochrome c Oxidase Collects Four Pumping Proton Equivalents in Each Catalytic Cycle

Yano¹,

Muramoto

Shimada³

et al. 2016

Journal of Biological Chemistry

132

View full text Add to dashboard Cite

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“…The latter consists of heme a 3 and Cu B in close proximity (for a review of the structure and function of oxidases, see refs. [3][4][5][6][7][8][9][10]. The A-family bacterial oxidases harbor two functional proton pathways leading from the n-side surface toward the catalytic site.…”

mentioning

confidence: 99%

Mutation of a single residue in the ba ₃ oxidase specifically impairs protonation of the pump site

Ballmoos

Gonska

Lachmann

et al. 2015

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

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The ba 3 -type cytochrome c oxidase from Thermus thermophilus is a membrane-bound protein complex that couples electron transfer to O 2 to proton translocation across the membrane. To elucidate the mechanism of the redox-driven proton pumping, we investigated the kinetics of electron and proton transfer in a structural variant of the ba 3 oxidase where a putative "pump site" was modified by replacement of Asp372 by Ile. In this structural variant, proton pumping was uncoupled from internal electron transfer and O 2 reduction. The results from our studies show that proton uptake to the pump site (time constant ∼65 μs in the wild-type cytochrome c oxidase) was impaired in the Asp372Ile variant. Furthermore, a reaction step that in the wild-type cytochrome c oxidase is linked to simultaneous proton uptake and release with a time constant of ∼1.2 ms was slowed to ∼8.4 ms, and in Asp372Ile was only associated with proton uptake to the catalytic site. These data identify reaction steps that are associated with protonation and deprotonation of the pump site, and point to the area around Asp372 as the location of this site in the ba 3 cytochrome c oxidase.cytochrome c oxidase | membrane protein | respiration | cytochrome aa 3 | electron transfer

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“…F transition. Most likely, the D-pathway facilitates proton transfer to a site other than the O 2 reduction site in addition to the proton transfer to the O 2 reduction site [69]. Furthermore, if Glu242 transfers protons to the propionate as discussed above, followed by the proton transfer to the O 2 reduction site giving the P !…”

Section: Experimental Results Suggesting That Both Chemical and Pumpementioning

confidence: 95%

Respiratory Conservation of Energy with Dioxygen: Cytochrome c Oxidase

Shimada¹,

Shinzawa‐Itoh²

2014

Sustaining Life on Planet Earth: Metalloenzymes Mastering Dioxygen and Other Chewy Gases

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Cytochrome c oxidase (CcO) is the terminal oxidase of cell respiration which reduces molecular oxygen (O₂) to H2O coupled with the proton pump. For elucidation of the mechanism of CcO, the three-dimensional location and chemical reactivity of each atom composing the functional sites have been extensively studied by various techniques, such as crystallography, vibrational and time-resolved electronic spectroscopy, since the X-ray structures (2.8 Å resolution) of bovine and bacterial CcO have been published in 1995.X-ray structures of bovine CcO in different oxidation and ligand binding states showed that the O₂reduction site, which is composed of Fe (heme a 3) and Cu (CuB), drives a non-sequential four-electron transfer for reduction of O₂to water without releasing any reactive oxygen species. These data provide the crucial structural basis to solve a long-standing problem, the mechanism of the O₂reduction.Time-resolved resonance Raman and charge translocation analyses revealed the mechanism for coupling between O₂reduction and the proton pump: O₂is received by the O₂reduction site where both metals are in the reduced state (R-intermediate), giving the O₂-bound form (A-intermediate). This is spontaneously converted to the P-intermediate, with the bound O₂fully reduced to 2 O²⁻. Hereafter the P-intermediate receives four electron equivalents from the second Fe site (heme a), one at a time, to form the three intermediates, F, O, and E to regenerate the R-intermediate. Each electron transfer step from heme a to the O₂reduction site is coupled with the proton pump.X-ray structural and mutational analyses of bovine CcO show three possible proton transfer pathways which can transfer pump protons (H) and chemical (water-forming) protons (K and D). The structure of the H-pathway of bovine CcO indicates that the driving force of the proton pump is the electrostatic repulsion between the protons on the H-pathway and positive charges of heme a, created upon oxidation to donate electrons to the O₂reduction site. On the other hand, mutational and time-resolved electrometric findings for the bacterial CcO strongly suggest that the D-pathway transfers both pump and chemical protons. However, the structure for the proton-gating system in the D-pathway has not been experimentally identified. The structural and functional diversities in CcO from various species suggest a basic proton pumping mechanism in which heme a pumps protons while heme a 3 reduces O₂as proposed in 1978.

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Functions of the hydrophilic channels in protonmotive cytochrome c oxidase

Cited by 93 publications

References 136 publications

The Mg2+-containing Water Cluster of Mammalian Cytochrome c Oxidase Collects Four Pumping Proton Equivalents in Each Catalytic Cycle

The Mg2+-containing Water Cluster of Mammalian Cytochrome c Oxidase Collects Four Pumping Proton Equivalents in Each Catalytic Cycle

Mutation of a single residue in the ba ₃ oxidase specifically impairs protonation of the pump site

Respiratory Conservation of Energy with Dioxygen: Cytochrome c Oxidase

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Functions of the hydrophilic channels in protonmotive cytochrome c oxidase

Cited by 93 publications

References 136 publications

The Mg2+-containing Water Cluster of Mammalian Cytochrome c Oxidase Collects Four Pumping Proton Equivalents in Each Catalytic Cycle

The Mg2+-containing Water Cluster of Mammalian Cytochrome c Oxidase Collects Four Pumping Proton Equivalents in Each Catalytic Cycle

Mutation of a single residue in the ba 3 oxidase specifically impairs protonation of the pump site

Respiratory Conservation of Energy with Dioxygen: Cytochrome c Oxidase

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Mutation of a single residue in the ba ₃ oxidase specifically impairs protonation of the pump site