Primary intermediate in the reaction of mixed-valence cytochrome c oxidase with oxygen.
The reaction of dioxygen with mixed-valence cytochrome c oxidase was followed in a rapid-mixing continuous-flow apparatus. The optical absorption difference spectrum and a kinetic analysis confirm the presence of the primary oxygen intermediate in the 0-100-microseconds time window. The resonance Raman spectrum of the iron-dioxygen stretching mode (568 cm-1) supplies evidence that the degree of electron transfer from the iron atom to the dioxygen is similar to that in oxy complexes of other heme proteins. Thus, the Fe-O2 bond does not display any unique structural features that could account for the rapid reduction of dioxygen to water. Furthermore, the frequency of the iron-dioxygen stretching mode is the same as that of the primary intermediate in the fully reduced enzyme, indicating that the oxidation state of cytochrome a plays no role in controlling the initial properties of the oxygen binding site.
Han
S
S
AT&T Bell Laboratories, Murray Hill, New Jersey 07974.
Ching
Y C
YC
Rousseau
D L
DL
D055598:Chemical Phenomena; D002621:Chemistry; D003576:Electron Transport Complex IV / Q000378:metabolism*; D007700:Kinetics; D010100:Oxygen / Q000378:metabolism*; D013057:Spectrum Analysis; D013059:Spectrum Analysis, Raman
D003576:Electron Transport Complex IV; D010100:Oxygen