The structure of the cytochrome a3-CuB site of mammalian cytochrome c oxidase as probed by MCD and EPR spectroscopy.
The nature of the complexes formed between cytochrome c oxidase and the three inhibitory ligands N3-, CN-, and S2- have been investigated by a combination of MCD and EPR spectroscopy. CN- forms a linear bridge between the Fe III a3 and CuB II, suggesting that the distance between these centers in the oxidized enzyme is between 5 and 5.25 A. This distance is too short to permit N3- to form a linear bridge and the evidence suggests this to be bent. In contrast S2- or SH- is unable to form any bridge and it seems likely that two SH- ions are bound by the bimetallic site, one to Fe III a3 and the other to CuB I. The significance of the a3-CuB distance in terms of oxygen binding and reduction is discussed.
Thomson
A J
AJ
Greenwood
C
C
Gadsby
P M
PM
Peterson
J
J
Eglinton
D G
DG
Hill
B C
BC
Nicholls
P
P
D001386:Azides / Q000494:pharmacology; D001665:Binding Sites; D055598:Chemical Phenomena; D002621:Chemistry; D002942:Circular Dichroism; D003300:Copper / Q000378:metabolism*; D003486:Cyanides / Q000494:pharmacology; D004578:Electron Spin Resonance Spectroscopy; D003576:Electron Transport Complex IV / Q000037:antagonists & inhibitors / Q000378:metabolism*; D005290:Ferric Compounds / Q000378:metabolism; D008786:Metmyoglobin / Q000031:analogs & derivatives / Q000378:metabolism; D013440:Sulfides / Q000494:pharmacology
D001386:Azides; D003486:Cyanides; D005290:Ferric Compounds; D013440:Sulfides; C007177:cyanometmyoglobin; C292386:metmyoglobin azide; C045784:metmyoglobin sulfide; D008786:Metmyoglobin; D003300:Copper; D003576:Electron Transport Complex IV