Low-temperature studies of electron transfer between different cytochromes c and cytochrome c oxidase

Biochemistry ◽  
1978 ◽  
Vol 17 (11) ◽  
pp. 2246-2249 ◽  
Author(s):  
Shelagh Ferguson-Miller ◽  
David L. Brautigan ◽  
Britton Chance ◽  
Alan Waring ◽  
E. Margoliash
Keyword(s):  
Electron Transfer ◽  
Low Temperature ◽  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Cytochromes C

scholarly journals Spectroscopic evidence for the participation of compound A (Fea32+-O2) in the reaction of mixed-valence cytochrome c oxidase with oxygen at room temperature

1983 ◽  
Vol 215 (3) ◽  
pp. 659-667 ◽  
Author(s):  
B C Hill ◽  
C Greenwood
Keyword(s):  
Electron Transfer ◽  
Low Temperature ◽  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Valence State ◽  
Room Temperature ◽  
Mixed Valence ◽  
Compound A ◽  
Mixed Valence State ◽  
Fast Phase

1. The reaction of the partially reduced mixed-valence state of cytochrome c oxidase (a3+CuA2+a3(2+)COCuB+) with O2 was studied by the rapid-reaction technique of flow-flash spectrophotometry at room temperature. Biphasic absorption records are observed in the time range up to 2 ms in both the Soret and visible spectral regions. The fast-phase rate is O2-concentration-dependent and reaches a pseudo-first-order value of 4.5 X 10(4)s-1 at 680 microM-O2 at 20 degrees C. Under the same conditions the second-phase rate is limited at 6.0 X 10(3)s-1. Kinetic difference spectra of the two species in the Soret region are not markedly different in form, whereas in the visible region two spectroscopically different species are clearly distinguished. 4. The first intermediate has a peak at 595 nm and a trough at 605 nm. The form of this spectrum resembles that seen in low-temperature studies and assigned to an O2-bound form of ferrocytochrome a3. This evidence supports a structure for oxycytochrome c oxidase with O2 bound only to cytochrome a3 and not bridged between cytochrome a3 and CuB. The second intermediate has a difference spectrum with a trough at 592 nm and a peak at 610 nm. Again, the form of this spectrum is similar to that observed during the O2 reaction at low temperature and is though to be a result of electron transfer from the oxidase to bound O2. 5. The oxygen profile of the fast phase suggests that a spectroscopically silent species may precede the formation of compound A. These data represent the first spectroscopic distinction, in the physiological temperature range, between O2 binding and electron transfer during the O2 reaction of mammalian cytochrome c oxidase. 6. A mechanism is presented for the O2 reaction of the mixed-valence state of cytochrome c oxidase involving four intermediate species. Electron transfer during this reaction is slow, relative to that seen with the fully reduced enzyme, and probably accounts for the detectability of the oxyferro species under these conditions.

Electron transfer from cytochrome c to 8-azido-ATP-modified cytochrome c oxidase

Biochemistry ◽  
1995 ◽  
Vol 34 (19) ◽  
pp. 6335-6343 ◽  
Author(s):  
Jian Lin ◽  
Shuguang Wu ◽  
Sunney I. Chan
Keyword(s):  
Electron Transfer ◽  
Cytochrome C ◽  
Cytochrome C Oxidase

Sulphide as an inhibitor and electron donor for the cytochrome c oxidase system

1982 ◽  
Vol 60 (6) ◽  
pp. 613-623 ◽  
Author(s):  
P. Nicholls ◽  
J.-K. Kim
Keyword(s):  
Cytochrome C ◽  
Oxygen Uptake ◽  
Cytochrome C Oxidase ◽  
Submitochondrial Particles ◽  
Inhibitory Interaction ◽  
Cytochromes C ◽  
Subsequent Step ◽  
Oxidase Enzyme ◽  
Rapid Reaction ◽  
The One

Anomalies both kinetic and equilibrium in nature are described for the inhibition of cytochrome c oxidase activity by sulphide in the isolated enzyme and in submitochondrial particles. These anomalies are related to the involvement of more than 1 mol of sulphide in the blockage of one cytochrome aa3 centre. Sulphide reduces resting cytochrome a3, a reaction that results in oxygen uptake and the loss of a sulphide molecule. Sulphide can also reduce cytochromes c and a; in the former case, a part of the one-equivalent oxidation product, presumed to be the SH∙ radical, reacts with oxygen. Such oxygen uptake is also seen under aerobic conditions when ferricyanide reacts with sulphide. Three phases are identified in the inhibitory interaction of sulphide with the cytochrome c oxidase enzyme itself: an initial rapid reaction involving sulphide oxidation, oxygen uptake, and conversion of cytochrome aa3 into the low-spin "oxyferri" form; a subsequent step in which sulphide reduces cytochrome a; and the final inhibitory step in which a third molecule of sulphide binds the a3 iron centre in the cytochrome [Formula: see text] (oxy) species to give cytochrome [Formula: see text]. The initial events parallel some of the events in the interaction of the cytochrome c – cytochrome aa3 system with monothiols; the final inhibitory event resembles that with cyanide.

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