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, 2005 (21). pp. 3501-3506. ISSN 1477-9226

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Abstract

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 Faculty of Science > School of Chemistry (former - to 2024)
UEA Research Groups:	Faculty of Science > Research Groups > Biophysical Chemistry (former - to 2017)
Depositing User:	Vishal Gautam
Date Deposited:	27 Jun 2005
Last Modified:	24 Sep 2024 09:59
URI:	https://ueaeprints.uea.ac.uk/id/eprint/17501
DOI:	10.1039/b501846c

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