Potentiometric titration of cytochrome‐bo type quinol oxidase of Escherichia coli: Evidence for heme‐heme and copper‐heme interaction

FEBS Letters

Ingledew, W.John¹  Salerno, John C.¹  Bolgiano, Barbara¹ 

[1] Department of Biochemistry and Microbiology, University of St. Andrews, St. Andrews, Scotland

关键词: Quinol oxidase;    Potentiometric titration;    Heme-heme interaction;    Coppes-heme interaction;   

DOI  :  10.1016/0014-5793(89)81249-9

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

The cytochrome-bo quinol oxidase of Escherichia coli contains a high-spin b-type heme (cytochrome o), a low-spin b-type heme (cytochrome b) and copper. The EPR signal from cytochrome o is axial high spin and when titrated potentiometrically gives a bell-shaped curve. The low-potential side of this curve (E _m7 approx. 160 mV) corresponds to the reduction/oxidation of the cytochrome. The high-potential side (E _m7 approx. 350 mV) is proposed to be due to reduction/oxidation of a copper center; in the CuII form tight cytochrome o-copper spin coupling results in a net even spin system and loss of the EPR spectrum. Optical spectra of the α-bands of the reduced cytochromes at 77 K show that cytochrome b has its maxima at 564 nm when cytochrome o is oxidized but that this shifts to 561 nm when cytochrome o (max. 555 nm) is reduced. Both a heme-copper (cytochrome o-CuII) and a heme-heme (cytochrome o-cytochrome b) interaction are indicated in this quinol oxidase. These results indicate that cytochrome-bo quinol oxidase has a binuclear heme-copper catalytic site and suggest striking structural similarity to subunit I of the cytochrome aa ₃ system.

【 授权许可】

Unknown