Abstract
It is shown that the oxidized form of the hexa-haem nitrite reductase of Wolinella succinogenes exists in two structurally and functionally distinct forms, termed 'resting' and 'redox-cycled'. The nitrite reductase as initially isolated, termed 'resting', has five low-spin ferrihaem groups and one high-spin ferrihaem group. The reduction of these haem groups by Na2S2O4 occurs in two kinetically and spectrally distinct phases. In the slower phase the haem groups are reduced by dithionite with a limiting rate of 4 s-1. If the enzyme is re-oxidized after reduction with dithionite or with methyl viologen, the resulting ferric form, termed 'redox-cycled', possesses only low-spin haem centres and a rate of reduction in the slower phase that is no longer limited. In the resting form of the enzyme the high-spin ferrihaem group is weakly exchange-coupled to a low-spin haem group. It is proposed that in the redox-cycled form the exchange coupling occurs between two low-spin ferric haem groups. This change in spin state allows a more rapid rate of electron transfer to the coupled pair.
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Selected References
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- Antonini E., Brunori M., Colosimo A., Greenwood C., Wilson M. T. Oxygen "pulsed" cytochrome c oxidase: functional properties and catalytic relevance. Proc Natl Acad Sci U S A. 1977 Aug;74(8):3128–3132. doi: 10.1073/pnas.74.8.3128. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Blackmore R. S., Brittain T., Gadsby P. M., Greenwood C., Thomson A. J. Electron paramagnetic resonance and magnetic circular dichroism studies of a hexa-heme nitrite reductase from Wolinella succinogenes. FEBS Lett. 1987 Jul 13;219(1):244–248. doi: 10.1016/0014-5793(87)81225-5. [DOI] [PubMed] [Google Scholar]
- Blackmore R. S., Gadsby P. M., Greenwood C., Thomson A. J. Spectroscopic studies of partially reduced forms of Wolinella succinogenes nitrite reductase. FEBS Lett. 1990 May 21;264(2):257–262. doi: 10.1016/0014-5793(90)80262-h. [DOI] [PubMed] [Google Scholar]
- Blackmore R., Brittain T. Kinetic studies on the nitrite reductase of Wolinella succinogenes. Biochem J. 1986 Jan 15;233(2):553–557. doi: 10.1042/bj2330553. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Blackmore R., Roberton A. M., Brittain T. The purification and some equilibrium properties of the nitrite reductase of the bacterium Wolinella succinogenes. Biochem J. 1986 Jan 15;233(2):547–552. doi: 10.1042/bj2330547. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Eglinton D. G., Johnson M. K., Thomson A. J., Gooding P. E., Greenwood C. Near-infrared magnetic and natural circular dichroism of cytochrome c oxidase. Biochem J. 1980 Nov 1;191(2):319–331. doi: 10.1042/bj1910319. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Foote N., Peterson J., Gadsby P. M., Greenwood C., Thomson A. J. A study of the oxidized form of Pseudomonas aeruginosa cytochrome c-551 peroxidase with the use of magnetic circular dichroism. Biochem J. 1984 Oct 15;223(2):369–378. doi: 10.1042/bj2230369. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Lambeth D. O., Palmer G. The kinetics and mechanism of reduction of electron transfer proteins and other compounds of biological interest by dithionite. J Biol Chem. 1973 Sep 10;248(17):6095–6103. [PubMed] [Google Scholar]
- Thomson A. J., Johnson M. K. Magnetization curves of haemoproteins measured by low-temperature magnetic-circular-dichroism spectroscopy. Biochem J. 1980 Nov 1;191(2):411–420. doi: 10.1042/bj1910411. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Wilson M. T., Peterson J., Antonini E., Brunori M., Colosimo A., Wyman J. A plausible two-state model for cytochrome c oxidase. Proc Natl Acad Sci U S A. 1981 Nov;78(11):7115–7118. doi: 10.1073/pnas.78.11.7115. [DOI] [PMC free article] [PubMed] [Google Scholar]