The anaerobic interaction of ferrocytochrome c with the “ferric” and “oxygenated” forms of purified cytochrome c oxidase. XVI. Cytochrome oxidase and its derivatives

1970 ◽  
Vol 197 (1) ◽  
pp. 1-10 ◽  
Author(s):  
R. Lemberg ◽  
M.E. Cutler
Keyword(s):  
Cytochrome C ◽  
Cytochrome Oxidase ◽  
Cytochrome C Oxidase ◽  
Ferrocytochrome C

scholarly journals Cyanide inhibition of cytochrome c oxidase. A rapid-freeze e.p.r. investigation

1984 ◽  
Vol 224 (3) ◽  
pp. 829-837 ◽  
Author(s):  
P Jensen ◽  
M T Wilson ◽  
R Aasa ◽  
B G Malmström
Keyword(s):  
Cytochrome C ◽  
Cytochrome Oxidase ◽  
Cytochrome C Oxidase ◽  
Partial Reduction ◽  
Bridging Ligand ◽  
Ferrocytochrome C ◽  
Cyanide Binding ◽  
Cyanide Inhibition

The inhibition of cytochrome c oxidase by cyanide, starting either with the resting or the pulsed enzyme, was studied by rapid-freeze quenching followed by quantitative e.p.r. It is found that a partial reduction of cytochrome oxidase by transfer of 2 electron equivalents from ferrocytochrome c to cytochrome a and CuA will induce a transition from a closed to an open enzyme conformation, rendering the cytochrome a3-CuB site accessible for cyanide binding, possibly as a bridging ligand. A heterogeneity in the enzyme is observed in that an e.p.r. signal from the cytochrome a3 3+-HCN complex is only found in 20% of the molecules, whereas the remaining cyanide-bound a3-CuB sites are e.p.r.-silent.

Optimum pH and ionic strength for the assay of cytochrome c oxidase from pea cotyledon mitochondria

1977 ◽  
Vol 55 (10) ◽  
pp. 1114-1117 ◽  
Author(s):  
Gerrit H. Bomhoff ◽  
Mary Spencer
Keyword(s):  
Ionic Strength ◽  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Ferrocytochrome C ◽  
Optimum Ph ◽  
Triton X ◽  
Assay Conditions ◽  
Nonionic Detergents

Cytochrome c oxidase (EC 1.9.3.1) has been solubilized by use of the nonionic detergents Triton X-114 and Triton X-100, from pea cotyledon mitochondria. Optimum assay conditions were determined for the oxidation of ferrocytochrome c in air. The results indicate that the plant cytochrome c oxidase resembles mammalian preparations in its sensitivity towards ionic strength and pH of the assay buffer.

scholarly journals Circular-dichroic properties and secondary structure of Pseudomonas aeruginosa soluble cytochrome c oxidase

1984 ◽  
Vol 218 (3) ◽  
pp. 907-912 ◽  
Author(s):  
M G Tordi ◽  
M C Silvestrini ◽  
A Colosimo ◽  
S Provencher ◽  
M Brunori
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Secondary Structure ◽  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Visible Region ◽  
Alpha Helix ◽  
Careful Analysis ◽  
Amino Acid Residues ◽  
Ferrocytochrome C ◽  
Significant Difference

The c.d. spectra of Pseudomonas aeruginosa cytochrome c oxidase in the oxidized state and the reduced state are reported in the visible- and u.v. absorption regions. In the visible region the comparison between the spectra of reduced cytochrome c oxidase and ferrocytochrome c-551 allows the identification of the c.d. bands mainly due to the d1 haem chromophore in cytochrome c oxidase. In the near-u.v. region the assignment of some of the observed peaks to the haem groups and to the aromatic amino acid residues is proposed. A careful analysis of the data in the far-u.v. region leads to the determination of the relative amounts of alpha-helix and beta-sheet in the enzyme, giving for the first time a picture of its secondary structure. A significant difference in this respect between the reduced and the oxidized species is observed and discussed in the light of similar conclusions reported by other workers.

The Conformational States of Oxidized and Oxygenated Beef-Heart Cytochrome c Oxidase

1975 ◽  
Vol 53 (4) ◽  
pp. 461-466 ◽  
Author(s):  
Jack A. Kornblatt ◽  
D. I. C. Kells ◽  
G. R. Williams
Keyword(s):  
Ascorbic Acid ◽  
Cytochrome C ◽  
Cytochrome Oxidase ◽  
Cytochrome C Oxidase ◽  
Sedimentation Velocity ◽  
Beef Heart ◽  
Conformational States

1. The "oxygenated" form of cytochrome oxidase has been generated by treatment of the enzyme with ascorbic acid.2. "Oxygenated oxidase" so generated is stable over long periods (24 h).3. Sedimentation velocity experiments have shown the "oxygenated oxidase to be a less compact molecule than the oxidized.

scholarly journals Limited-turnover studies on proton translocation in reconstituted cytochrome c oxidase-containing vesicles

1979 ◽  
Vol 182 (1) ◽  
pp. 149-156 ◽  
Author(s):  
R P Casey ◽  
J B Chappell ◽  
A Azzi
Keyword(s):  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Proton Pump ◽  
Proton Translocation ◽  
Strong Support ◽  
Ferrocytochrome C ◽  
Vesicle Membranes ◽  
Careful Control ◽  
Hydrogen Carrier ◽  
Reconstituted System

We have investigated ferrocytochrome c-induced proton ejection from reconstituted cytochrome c oxidase-containing vesicles using careful control of the number of enzyme turnovers. Ferrocytochrome c caused the appearance of protons at the vesicle exterior, and this could be abolished by using a protonophore. In addition, its decay was dependent on the permeability of the vesicle membranes to protons and the number of turnovers of the oxidase. These observations indicate that the ejection of protons was the result of genuine translocation. The possibility of this translocation occurring via a Mitchellian loop as a result of the presence of a reduced hydrogen carrier contaminating the enzyme was considered and excluded. Proton-translocating activity in this reconstituted system depended critically on the ratio of enzyme to lipid used in the reconstitution process and we propose a rationale to account for this. We conclude that our data provide strong support for the proposal that cytochrome c oxidase acts as a proton pump and that approx. 0.9 H+ is excluded per ferrocytochrome c molecule oxidized.

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.

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