Conformations of oxidized cytochrome c oxidase

Gary W Brudvig, Tom H. Stevens, Randall H. Morse, Sunney I. Chan

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Abstract

Oxidized cytochrome c oxidase is shown to exist in three conformations in addition to the transient "g5" conformation previously reported [Shaw, R. W., Hansen, R. E., & Beinert, H. (1978) J. Biol. Chem. 253, 6637-6640]. The "resting" and "g12" conformations are distinguished by an NO-induced cytochrome a3 electron paramagnetic resonance (EPR) signal and an EPR signal at g′ = 12, respectively. The "oxygenated" conformation exhibits an unusual EPR signal in the presence of fluoride and is identical with the "oxygenated" state first discovered by Okunuki et al. [Okunuki, K., Hagihora, B., Sekuzu, I., & Horio, T. (1958) Proc. Int. Symp. Enzyme Chem., Tokyo, Kyoto, 264]. It is proposed that when the reduced enzyme is reoxidized by dioxygen, the oxidized enzyme first relaxes from the "g5" into the "oxygenated" conformation after which a percentage of the molecules slowly relax into the "g12" conformation. The "resting" conformation is not formed when the enzyme is reoxidized. On the basis of the EPR observations, it is proposed that these various conformations of the oxidized enzyme differ in the structure of the cytochrome a3-Cua3 site. Structures for the cytochrome a3-Cua3 site are proposed for each conformation, and a mechanism by which these conformations undergo interconversion among themselves is described.

Original languageEnglish
Pages (from-to)3912-3921
Number of pages10
JournalBiochemistry
Volume20
Issue number13
Publication statusPublished - 1981

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Electron Transport Complex IV
Cytochromes a3
Electron Spin Resonance Spectroscopy
Conformations
Enzymes
Paramagnetic resonance
Tokyo
Fluorides
Oxygen
Molecules

ASJC Scopus subject areas

  • Biochemistry

Cite this

Brudvig, G. W., Stevens, T. H., Morse, R. H., & Chan, S. I. (1981). Conformations of oxidized cytochrome c oxidase. Biochemistry, 20(13), 3912-3921.

Conformations of oxidized cytochrome c oxidase. / Brudvig, Gary W; Stevens, Tom H.; Morse, Randall H.; Chan, Sunney I.

In: Biochemistry, Vol. 20, No. 13, 1981, p. 3912-3921.

Research output: Contribution to journalArticle

Brudvig, GW, Stevens, TH, Morse, RH & Chan, SI 1981, 'Conformations of oxidized cytochrome c oxidase', Biochemistry, vol. 20, no. 13, pp. 3912-3921.
Brudvig GW, Stevens TH, Morse RH, Chan SI. Conformations of oxidized cytochrome c oxidase. Biochemistry. 1981;20(13):3912-3921.
Brudvig, Gary W ; Stevens, Tom H. ; Morse, Randall H. ; Chan, Sunney I. / Conformations of oxidized cytochrome c oxidase. In: Biochemistry. 1981 ; Vol. 20, No. 13. pp. 3912-3921.
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N2 - Oxidized cytochrome c oxidase is shown to exist in three conformations in addition to the transient "g5" conformation previously reported [Shaw, R. W., Hansen, R. E., & Beinert, H. (1978) J. Biol. Chem. 253, 6637-6640]. The "resting" and "g12" conformations are distinguished by an NO-induced cytochrome a3 electron paramagnetic resonance (EPR) signal and an EPR signal at g′ = 12, respectively. The "oxygenated" conformation exhibits an unusual EPR signal in the presence of fluoride and is identical with the "oxygenated" state first discovered by Okunuki et al. [Okunuki, K., Hagihora, B., Sekuzu, I., & Horio, T. (1958) Proc. Int. Symp. Enzyme Chem., Tokyo, Kyoto, 264]. It is proposed that when the reduced enzyme is reoxidized by dioxygen, the oxidized enzyme first relaxes from the "g5" into the "oxygenated" conformation after which a percentage of the molecules slowly relax into the "g12" conformation. The "resting" conformation is not formed when the enzyme is reoxidized. On the basis of the EPR observations, it is proposed that these various conformations of the oxidized enzyme differ in the structure of the cytochrome a3-Cua3 site. Structures for the cytochrome a3-Cua3 site are proposed for each conformation, and a mechanism by which these conformations undergo interconversion among themselves is described.

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