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