Peroxide‐induced spectral perturbations of the 280‐nm absorption band of cytochrome c oxidase

FEBS Letters

Larsen, Randy W.¹ 

[1] Department of Chemistry, University of Hawaii at Manoa, 2545 The Mall, Honolulu, HI 96822, USA

关键词: Cytochrome oxidase;    Hydrogen peroxide;    Proton pump;    Compound C;    Oxyferryl complex;    Hydrogen peroxide;   

DOI  :  10.1016/0014-5793(94)00999-6

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

It is now widely believed that the first two electrons transferred to the dioxygen reduction site in cytochrome c oxidase (CcO) are not coupled to proton translocation. The activation of the pump cycle correlates with the binding of dioxygen to the binuclear center. In order to investigate conformational changes in CcO associated with the formation of dixoygen intermediates during the catalytic cycle of CcO, the effects of hydrogen peroxide binding to CcO have been examined using UV optical absorption and second derivative techniques. Our data indicates that in the presence low concentrations of H₂O₂ (2:1 molar ratio) an initial CcO-peroxide species is formed in which the 280-nm absorption band is red shifted. This red shift occurs prior to spectral changes associated with H₂O₂ binding to cytochrome a ₃. Upon addition of higher concentrations of H₂O₂ (⪢10 equivalents of H₂O₂ per equivalent of CcO) oxidized CcO is converted to F-state enzyme with no corresponding shift at 280 nm. It is suggested that H₂O₂ initially binds to Cu²⁺ _B resulting in a conformational change in the enzyme giving rise to a red-shifted 280 nm band. The absence of any conformational changes in F-state enzyme is consistent with the lack of bridging interactions with Cu²⁺ _B in this intermediate.

【 授权许可】

Unknown