scholarly journals Structural insights into electron transfer in caa3-type cytochrome oxidase

Nature ◽  
2012 ◽  
Vol 487 (7408) ◽  
pp. 514-518 ◽  
Author(s):  
Joseph A. Lyons ◽  
David Aragão ◽  
Orla Slattery ◽  
Andrei V. Pisliakov ◽  
Tewfik Soulimane ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Cytochrome Oxidase ◽  
Structural Insights

STUDIES ON THE CYTOCHROME OXIDASE AND OXIDATION PATHWAY IN UREDOSPORES OF WHEAT STEM RUST

1961 ◽  
Vol 39 (5) ◽  
pp. 1131-1148 ◽  
Author(s):  
G. A. White ◽  
G. A. Ledingham
Keyword(s):  
Electron Transfer ◽  
Cytochrome C ◽  
Cytochrome Oxidase ◽  
Reductase Activity ◽  
Oxygen Affinity ◽  
Antimycin A ◽  
Respiratory Enzymes ◽  
Wheat Stem Rust ◽  
Malic Dehydrogenase ◽  
Cytochrome C Reductase

Electron transport to oxygen in a particulate fraction from uredospores of Puccinia graminis var. tritici occurs through a series of carriers similar to those of other fungi and higher plants.Experiments with various enzyme inhibitors and measurements of the oxygen affinity of respiration have shown that cytochrome oxidase mediates the final step in the sequence of electron transfer. The enzyme was localized in a fraction sedimenting at 20,000 g and was typically inhibited by cyanide, azide, and CO-dark, the latter inhibition being light-reversible. Other enzymes present were succinic-cytochrome c reductase, DPNH- and TPNH-cytochrome c reductase, dye reductase, malic dehydrogenase, isocitric dehydrogenase, and glycerol-1-phosphate dehydrogenase. Particulates failed to oxidize DPNH unless an electron acceptor was added. An increase in the activity of several of the respiratory enzymes was noted upon spore germination.Succinic-cytochrome c reductase was only partially sensitive to Antimycin A, HOQNO, and the naphthoquinone, SN 5949. These compounds markedly inhibited a labile portion of the DPNH-cytochrome c reductase activity but had little effect on the stable activity remaining in aged particles. Menadione, but not vitamin K1, stimulated electron transfer. Antimycin A and SN 5949 virtually blocked spore respiration suggesting a "Slater-type" factor in the intact pathway of oxidation.

scholarly journals Studies on partially reduced mammalian cytochrome oxidase reactions with ferrocytochrome c

1976 ◽  
Vol 157 (3) ◽  
pp. 591-598 ◽  
Author(s):  
C Greenwood ◽  
T Brittain
Keyword(s):  
Electron Transfer ◽  
Cytochrome C ◽  
Cytochrome Oxidase ◽  
Transfer Reaction ◽  
Temperature Jump ◽  
Electron Transfer Reaction ◽  
Relaxation Processes ◽  
Stopped Flow ◽  
Rapid Reduction ◽  
Ferrocytochrome C

The kinetics of the electron-transfer process which occurs between ferrocytochrome c and partially reduced mammalian cytochrome oxidase were studied by the rapid spectrophotometric techniques of stopped flow and temperature jump. Stopped-flow experiments showed initial very fast extinction changes at 605 nm and at 563 nm, indicating the simultaneous reduction of cytochrome a and oxidation of ferrocytochrome c. During this ‘burst’ phase, say the first 50 ms after mixing, it was invariably found that more cytochrome c had been oxidized than cytochrome a had been reduced. This discrepancy in electron equivalents may be accounted for by the rapid reduction of another redox site in the enzyme, possibly that associated with the extinction changes observed at 830 nm. During the incubation period in which the partially reduced oxidase was prepared, the rate of reduction of cytochrome a by ferrocytochrome c, at constant reactant concentrations, decreased with time. Temperature-jump experiments showed the presence of two relaxation processes. The faster of the two phases was assigned to the electron-transfer reaction between cytochrome c and cytochrome a. A study of the concentration-dependence of the reciprocal relaxation time for this phase yielded a rate constant of 9 X 10(6)M-1-s-1 for the electron transfer from cytochrome c to cytochrome a, and a value of 8.5 X 10(6)M-1-s-1 for the reverse reaction. The equilibrium constant for the electron-transfer reaction is therefore close to unity. The slower phase has been interpreted as signalling the transfer of electrons between cytochrome a and another redox site within the oxidase molecule.

scholarly journals A temperature-jump study of the reaction between azurin and cytochrome c oxidase from Pseudomonas aeruginosa

1975 ◽  
Vol 151 (1) ◽  
pp. 185-188 ◽  
Author(s):  
M Brunori ◽  
S R Parr ◽  
C Greenwood ◽  
M T Wilson
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Electron Transfer ◽  
Cytochrome Oxidase ◽  
Cytochrome C Oxidase ◽  
Molecular Complex ◽  
Transfer Reaction ◽  
Temperature Jump ◽  
Electron Transfer Reaction ◽  
Internal Transfer ◽  
Rate Limiting

The electron-transfer reaction between azurin and the cytochrome oxidase from Pseudomonas aeruginosa was investigated by temperature-jump relaxation in the absence of O2 and in the presence of CO. The results show that: (i) reduced azurin exists in two forms in equilibrium, only one of which is capable of exchanging electrons with the Pseudomonas cytochrome oxidase, in agreement with M. T. Wilson, C. Greenwood, M. Brunori & E. Antonini (1975) (Biochem. J. 145, 449-457); (ii) the electron transfer between azurin and Pseudomonas cytochrome oxidase occurs within a molecular complex of the two proteins; this internal transfer becomes rate-limiting at high reagent concentrations.

Effect of diethyl pyrocarbonate modification on spectral and steady-state kinetic properties of bovine heart cytochrome oxidase

1992 ◽  
Vol 70 (7) ◽  
pp. 565-572
Author(s):  
John D. Doran ◽  
Bruce C. Hill
Keyword(s):  
Electron Transfer ◽  
Steady State ◽  
Cytochrome Oxidase ◽  
Proton Pumping ◽  
Kinetic Properties ◽  
High Turnover ◽  
Bovine Heart ◽  
Diethyl Pyrocarbonate ◽  
Steady State Kinetic ◽  
State Kinetic

The histidine-specific reagent diethyl pyrocarbonate has been used to chemically modify bovine heart cytochrome oxidase. Thirty-two of sixty-seven histidine residues of cytochrome oxidase are accessible to modification by diethyl pyrocarbonate. Effects on the Soret and α bands of the heme spectrum indicate disturbance in the environment of one or both of the heme groups. However, diethyl pyrocarbonate modification does not alter the 830-nm absorbance band, suggesting that the environment of CuA is unchanged. Maximal modification of cytochrome oxidase by diethyl pyrocarbonate results in loss of 85–90% of the steay-state electron transfer activity, which can be reversed by hydroxylamine treatment. However, modification of the first 20 histidines does not alter either activity or the heme spectrum, but only when 32 residues have been modified are the activity and heme spectral changes complete. The steady-state kinetic profile of fully modified oxidase is monophasic; the phase corresponding to tight cytochrome c binding and low turnover is retained, whereas the high turnover phase is abolished. Proteoliposomes incorporated with modified oxidase have a 65% lower respiratory control ratio and 40% lower proton pumping stoichiometry than liposomes containing unmodified oxidase. These results are discussed in terms of a redox-linked proton pumping model for energy coupling via cytochrome oxidase.Key words: cytochrome oxidase, histidine modification, electron transfer, proton pumping, diethyl pyrocarbonate.

Proton-Coupled Electron Transfer in Cytochrome Oxidase

2010 ◽  
Vol 110 (12) ◽  
pp. 7062-7081 ◽  
Author(s):  
Ville R. I. Kaila ◽  
Michael I. Verkhovsky ◽  
Mårten Wikström
Keyword(s):  
Electron Transfer ◽  
Cytochrome Oxidase ◽  
Proton Coupled Electron Transfer
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