scholarly journals A re-examination of the reactions of cyanide with cytochrome c oxidase

1984 ◽  
Vol 220 (1) ◽  
pp. 57-66 ◽  
Author(s):  
M G Jones ◽  
D Bickar ◽  
M T Wilson ◽  
M Brunori ◽  
A Colosimo ◽  
...  
Keyword(s):  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Essential Feature ◽  
Tight Binding ◽  
Sodium Dithionite ◽  
Difference Spectra ◽  
Ferrocytochrome C ◽  
Cyanide Binding ◽  
Kinetic Predictions ◽  
Reduced Forms

Experiments were performed to examine the cyanide-binding properties of resting and pulsed cytochrome c oxidase in both their stable and transient turnover states. Inhibition of the oxidation of ferrocytochrome c was monitored as a function of cyanide concentration. Cyanide binding to partially reduced forms produced by mixing cytochrome c oxidase with sodium dithionite was also examined. A model is presented that accounts fully for cyanide inhibition of the enzyme, the essential feature of which is the rapid, tight, binding of cyanide to transient, partially reduced, forms of the enzyme populated during turnover. Computer fitting of the experimentally obtained data to the kinetic predictions given by this model indicate that the cyanide-sensitive form of the enzyme binds the ligand with combination constants in excess of 10(6) M-1 X s-1 and with KD values of 50 nM or less. Kinetic difference spectra indicate that cyanide binds to oxidized cytochrome a33+ and that this occurs rapidly only when cytochrome a and CuA are reduced.

scholarly journals Kinetic studies on the binding of cyanide to oxygenated cytochrome c oxidase

1976 ◽  
Vol 155 (2) ◽  
pp. 453-455 ◽  
Author(s):  
T Brittain ◽  
C Greenwood
Keyword(s):  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Kinetic Studies ◽  
Binding Properties ◽  
Cyanide Concentration ◽  
Cyanide Binding ◽  
Single Process ◽  
Reduced Forms

The reaction of cyanide with oxygenated cytochrome c oxidase was followed by means of flow-flash techniques. The oxygenated form, produced after photolysis of the partially reduced CO complex in the presence of cyanide and O2, shows cyanide-binding properties distinct from those of both the oxidized and the reduced forms of the protein. The binding is a single process (k = 22M-1-S-1) linearly dependent on cyanide concentration to as high as 75 mM. It is suggested that the oxygenated form is a conformational variant of the oxidized protein.

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.

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