Evidence for two H2O2‐binding sites in ferric cytochrome c oxidase Indication to the O‐cycle?

FEBS Letters

Vygodina, Tatyana¹  Konstantinov, Alexander A.¹ 

[1] A.N. Belozersky Laboratory of Molecular Biology and Bioorganic Chemistry, Moscow State University, Moscow 119899, USSR

关键词: Cytochrome c oxidase;    Peroxide compound;    O-cycle;    Proteoliposome;    Spectral characteristic;    Proton pump;   

DOI  :  10.1016/0014-5793(87)80258-2

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

H₂O₂ addition to the oxidized cytochrome c oxidase reconstituted in liposomes brings about a red shift of the Soret band of the enzyme and an increased absorption in the visible region with two distinct peaks at ∼570 and 605 nm. Throughout pH range 6–8.5, the spectral changes at 570 nm and in the Soret band titrate with very similar pH-independent K _d values of 2–3,μM. At the same time, K _d of the peroxide complex measured at 605 nm increases markedly with increased H⁺ activity reaching the value of 18 ± 2 μM at pH 6.0. This finding may indicate the presence of two different H₂O₂-binding sites in the enzyme with different affinity for the ligand at acid pH. The Soret and 570 nm band effects are suggested to report H₂O₂ coordination to heme iron of a ₃, whereas the maximum at 605 nm could arise from H₂O₂ binding to Cu _a3 followed by the enzyme transition into the ‘pulsed’ (or ‘420/605’) conformation. Possible implication of the two H₂O₂-binding sites for the cytochrome oxidase redox and proton-pumping mechanisms are discussed.

【 授权许可】

Unknown