Formation of a cytochrome c–nitrous oxide reductase complex is obligatory for N2O reduction by Paracoccus pantotrophus

Rasmussen, Tim, Brittain, Thomas, Berks, Ben C., Watmough, Nicholas J. and Thomson, Andrew J. (2005) Formation of a cytochrome c–nitrous oxide reductase complex is obligatory for N2O reduction by Paracoccus pantotrophus. Dalton Transactions (21). pp. 3501-3506. ISSN 1477-9226

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Nitrous oxide reductase (N2OR) catalyses the final step of bacterial denitrification, the two-electron reduction of nitrous oxide (N2O) to dinitrogen (N2). N2OR contains two metal centers; a binuclear copper center, CuA, that serves to receive electrons from soluble donors, and a tetranuclear copper-sulfide center, CuZ, at the active site. Stopped flow experiments at low ionic strengths reveal rapid electron transfer (kobs = 150 s-1) between reduced horse heart (HH) cytochrome c and the CuA center in fully oxidized N2OR. When fully reduced N2OR was mixed with oxidized cytochrome c, a similar rate of electron transfer was recorded for the reverse reaction, followed by a much slower internal electron transfer from CuZ to CuA (kobs = 0.1–0.4 s-1). The internal electron transfer process is likely to represent the rate-determining step in the catalytic cycle. Remarkably, in the absence of cytochrome c, fully reduced N2OR is inert towards its substrate, even though sufficient electrons are stored to initiate a single turnover. However, in the presence of reduced cytochrome c and N2O, a single turnover occurs after a lag-phase. We propose that a conformational change in N2OR is induced by its specific interaction with cytochrome c that in turn either permits electron transfer between CuA and CuZ or controls the rate of N2O decomposition at the active site.

Item Type: Article
Faculty \ School: Faculty of Science > School of Biological Sciences
Faculty of Science > School of Chemistry
UEA Research Groups: Faculty of Science > Research Centres > Centre for Molecular and Structural Biochemistry
Faculty of Science > Research Groups > Molecular Microbiology
Faculty of Science > Research Groups > Biophysical Chemistry (former - to 2017)
Depositing User: Users 2731 not found.
Date Deposited: 17 May 2011 10:18
Last Modified: 29 May 2023 23:56
DOI: 10.1039/B501846C

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