Reaction mechanism and phospholipid structures of bovine heart cytochrome c oxidase

2005 ◽  
Vol 33 (5) ◽  
pp. 934-937 ◽  
Author(s):  
S. Yoshikawa
Keyword(s):  
Hydrogen Bond ◽  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Hydrogen Bond Network ◽  
X Ray ◽  
Bovine Heart ◽  
O2 Reduction ◽  
Bond Network ◽  
Electron Reduction ◽  
Enzyme Functions

Bovine heart cytochrome c oxidase is a large multi-component membrane protein containing several phospholipids. X-ray structures of this enzyme at high resolution, determined recently, show a trigonal planar structure of CuB site in the O2 reduction site, which could contribute critically to the four-electron reduction of O2 bound at haem a3, and a hydrogen bond network, through which the proton pump is driven by haem a. The possible roles of phospholipids in the enzyme functions are discussed.

scholarly journals Structures of bovine cytochrome oxidase reveal proton active transports

2014 ◽  
Vol 70 (a1) ◽  
pp. C1505-C1505
Author(s):  
Naomine Yano ◽  
Kyoko Shinzawa-Itoh ◽  
Atsuhiro Shimada ◽  
Shuhei Takemutra ◽  
Takako Kawahara ◽  
...  
Keyword(s):  
Hydrogen Bond ◽  
Electron Transfer ◽  
Cytochrome C ◽  
Water Channel ◽  
Proton Pumping ◽  
Hydrogen Bond Network ◽  
O2 Reduction ◽  
Bond Network ◽  
Full Occupancy ◽  
O2 Binding

Bovine cytochrome c oxidase (CcO) pumps four protons in each catalytic cycle through H-pathway including a hydrogen-bond network and a water channel in tandem. Protons, transferred through the water-channel from the negative side of mitochondrial inner membrane into the hydrogen-bond network, are pumped to the positive side of the membrane electrostatically by net positive charges on a heme (heme a) iron created upon electron transfer to the O2 reduction site. For blockage of backward proton leak from the hydrogen-bond network, which determines the proton-pumping direction, the water channel is closed after O2 binding to initiate proton-pump. Thus, four protons must be collected in the hydrogen-bond network before O2 binding. The X-ray structural analyses of the oxidized/reduced CcO at 1.5/1.6 Å resolution reveal a large cluster composed of ~21 water molecules and a Mg2+ site including Glu198 (Subunit II) bridging CuA and Mg2+. The cluster of the oxidized state have 20 water sites with full occupancy and two sites with partial occupies of water, while that of the reduced state have 19 water sites with full occupancy and 3 sites with partial occupancies. The carboxyl group of Glu198 changes its coordination structure to Mg2+ upon the reduction of the active centers. The cluster is tightly sealed sterically against proton exchanges with the cluster outside except for a short hydrogen-bond network connecting the cluster with H-pathway. Five proton-acceptable groups hydrogen-bonded with the cluster suggest sufficient storage capacity for four proton equivalents. The redox-coupled structural changes in the electron transfer pathway from CuA, the initial electron acceptor from cytochrome c, to heme a suggest redox-driven effective proton donations from the cluster to H-pathway, facilitated by Glu198. These results indicate that the cluster is a crucial element of the proton-pumping system of bovine CcO.

scholarly journals Effect of pressure on a mixed valence FeiiFeiii2complex

2014 ◽  
Vol 70 (a1) ◽  
pp. C901-C901
Author(s):  
Solveig Madsen ◽  
Jacob Overgaard ◽  
Bo Iversen
Keyword(s):  
Phase Transition ◽  
Hydrogen Bond ◽  
Mixed Valence ◽  
Hydrogen Bond Network ◽  
X Ray Diffraction ◽  
X Ray ◽  
Effect Of Pressure ◽  
Bond Network ◽  
Fe Sites ◽  
Cyano Groups

Intramolecular electron transfer (ET) in mixed valence (MV) oxo-centered [FeiiFeiii2O(carboxylate)6(ligand)3]·solvent complexes is highly dependent on temperature, on the nature of the ligands, and on the presence of crystal solvent molecules [1]. Whereas the effects of temperature, crystal solvent, and ligand variation on the details of the ET have been explored thoroughly, the effect of pressure is less well described [2]. The effect of pressure on the ET in MV Fe3O(cyanoacetate)6(water)3has been investigated with single crystal X-ray diffraction and Mössbauer spectroscopy. Previous multi-temperature studies have shown that at room temperature the ET between the three Fe sites is fast and the observed structure of the Fe3core is a perfectly equilateral triangle [3]. Cooling the complex below 130 K induces a phase transition as the ET slows down. Below 120 K the Fe3core is distorted due to the localization of the itinerant electron on one of the three Fe sites in the triangle (the complex is then in the valence trapped state). The valence trapping is complete within a temperature interval of just 10 K. The abruptness of the transition has been attributed to the extended hydrogen bond network involving water ligands and cyano groups, promoting intermolecular cooperative effects. The high-pressure X-ray diffraction data show that there is a 900flip of half the cyano groups at 3.5 GPa, which dramatically changes the hydrogen bond network. At a slightly higher pressure, a phase transition is found to occur. The five single crystals investigated all broke into minor fragments at the transition; however triclinic unit cells, similar to the low temperature unit cell, could be indexed from selected spots. Additional evidence that the complex is valence trapped comes from high pressure Mössbauer spectra measured above the phase transition (4 GPa). The relationship between valence trapping and the structural changes will in this work be highlighted using void space and Hirshfeld surface analysis.

X-ray Absorption Spectroscopy Study of the Hydrogen Bond Network in the Bulk Water of Aqueous Solutions

2005 ◽  
Vol 109 (27) ◽  
pp. 5995-6002 ◽  
Author(s):  
Lars-Åke Näslund ◽  
David C. Edwards ◽  
Philippe Wernet ◽  
Uwe Bergmann ◽  
Hirohito Ogasawara ◽  
...  
Keyword(s):  
Hydrogen Bond ◽  
Aqueous Solutions ◽  
Absorption Spectroscopy ◽  
Bulk Water ◽  
Hydrogen Bond Network ◽  
Spectroscopy Study ◽  
X Ray ◽  
Bond Network ◽  
X Ray Absorption

scholarly journals X-ray structures of catalytic intermediates of cytochrome c oxidase provide insights into its O2 activation and unidirectional proton-pump mechanisms

2020 ◽  
Vol 295 (17) ◽  
pp. 5818-5833
Author(s):  
Atsuhiro Shimada ◽  
Yuki Etoh ◽  
Rika Kitoh-Fujisawa ◽  
Ai Sasaki ◽  
Kyoko Shinzawa-Itoh ◽  
...  
Keyword(s):  
Hydrogen Bond ◽  
Resonance Raman Spectroscopy ◽  
Transmembrane Helix ◽  
Water Channel ◽  
Bound State ◽  
Proton Pumping ◽  
Hydrogen Bond Network ◽  
X Ray ◽  
Catalytic Intermediates ◽  
Bond Network

Cytochrome c oxidase (CcO) reduces O2 to water, coupled with a proton-pumping process. The structure of the O2-reduction site of CcO contains two reducing equivalents, Fea32+ and CuB1+, and suggests that a peroxide-bound state (Fea33+–O−–O−–CuB2+) rather than an O2-bound state (Fea32+–O2) is the initial catalytic intermediate. Unexpectedly, however, resonance Raman spectroscopy results have shown that the initial intermediate is Fea32+–O2, whereas Fea33+–O−–O−–CuB2+ is undetectable. Based on X-ray structures of static noncatalytic CcO forms and mutation analyses for bovine CcO, a proton-pumping mechanism has been proposed. It involves a proton-conducting pathway (the H-pathway) comprising a tandem hydrogen-bond network and a water channel located between the N- and P-side surfaces. However, a system for unidirectional proton-transport has not been experimentally identified. Here, an essentially identical X-ray structure for the two catalytic intermediates (P and F) of bovine CcO was determined at 1.8 Å resolution. A 1.70 Å Fe–O distance of the ferryl center could best be described as Fea34+ = O2−, not as Fea34+–OH−. The distance suggests an ∼800-cm−1 Raman stretching band. We found an interstitial water molecule that could trigger a rapid proton-coupled electron transfer from tyrosine-OH to the slowly forming Fea33+–O−–O−–CuB2+ state, preventing its detection, consistent with the unexpected Raman results. The H-pathway structures of both intermediates indicated that during proton-pumping from the hydrogen-bond network to the P-side, a transmembrane helix closes the water channel connecting the N-side with the hydrogen-bond network, facilitating unidirectional proton-pumping during the P-to-F transition.

scholarly journals Temperature dependence of the hydrogen bond network in trimethylamine N-oxide and guanidine hydrochloride–water solutions

2017 ◽  
Vol 19 (41) ◽  
pp. 28470-28475 ◽  
Author(s):  
Felix Lehmkühler ◽  
Yury Forov ◽  
Mirko Elbers ◽  
Ingo Steinke ◽  
Christoph J. Sahle ◽  
...  
Keyword(s):  
Hydrogen Bond ◽  
Temperature Dependence ◽  
Compton Scattering ◽  
Guanidine Hydrochloride ◽  
Hydrogen Bond Network ◽  
X Ray ◽  
Water Solutions ◽  
Scattering Study ◽  
Bond Network

We present an X-ray Compton scattering study on aqueous trimethylamine N-oxide (TMAO) and guanidine hydrochloride solutions (GdnHCl) as a function of temperature.

Tautomerism and hydrogen bonding in guaninium phosphite and guaninium phosphate salts

2007 ◽  
Vol 63 (3) ◽  
pp. 448-458 ◽  
Author(s):  
El-Eulmi Bendeif ◽  
Slimane Dahaoui ◽  
Nourredine Benali-Cherif ◽  
Claude Lecomte
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Crystal Structures ◽  
Monoclinic Space Group ◽  
Data Sets ◽  
Hydrogen Bond Network ◽  
Space Group ◽  
X Ray ◽  
Bond Network ◽  
Phosphate Salts

The crystal structures of three similar guaninium salts, guaninium monohydrogenphosphite monohydrate, C5H6N5O+·H2O3P−·H2O, guaninium monohydrogenphosphite dihydrate, C5H6N5O+·H2O3P−·2H2O, and guaninium dihydrogenmonophosphate monohydrate, C5H6N5O+·H2O4P−·H2O, are described and compared. The crystal structures have been determined from accurate single-crystal X-ray data sets collected at 100 (2) K. The two phosphite salts are monoclinic, space group P21/c, with different packing and the monophosphate salt is also monoclinic, space group P21/n. An investigation of the hydrogen-bond network in these guaninium salts reveals the existence of two ketoamine tautomers, the N9H form and an N7H form.

On the Origin of the Hydrogen-Bond-Network Nature of Water: X-Ray Absorption and Emission Spectra of Water-Acetonitrile Mixtures

2011 ◽  
Vol 50 (45) ◽  
pp. 10621-10625 ◽  
Author(s):  
Kathrin M. Lange ◽  
René Könnecke ◽  
Mikhail Soldatov ◽  
Ronny Golnak ◽  
Jan-Erik Rubensson ◽  
...  
Keyword(s):  
Hydrogen Bond ◽  
Emission Spectra ◽  
Hydrogen Bond Network ◽  
Absorption And Emission ◽  
X Ray ◽  
Absorption And Emission Spectra ◽  
Bond Network ◽  
X Ray Absorption
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