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Defining the Proton Entry Point in the Bacterial Respiratory Nitric-oxide Reductase
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
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2008 (English)In: Journal of Biological Chemistry, ISSN 0021-9258, Vol. 283, no 7, 3839-3845 p.Article in journal (Refereed) Published
Place, publisher, year, edition, pages
2008. Vol. 283, no 7, 3839-3845 p.
URN: urn:nbn:se:su:diva-25463DOI: 10.1074/jbc.M704615200ISI: 000253083500018OAI: diva2:199753
Part of urn:nbn:se:su:diva-8171Available from: 2008-09-25 Created: 2008-09-25 Last updated: 2009-05-12Bibliographically approved
In thesis
1. Nitric Oxide Reductase from Paracoccus denitrificans: A Proton Transfer Pathway from the “Wrong” Side
Open this publication in new window or tab >>Nitric Oxide Reductase from Paracoccus denitrificans: A Proton Transfer Pathway from the “Wrong” Side
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Denitrification is an anaerobic process performed by several soil bacteria as an alternative to aerobic respiration. A key-step in denitrification (the N-N-bond is made) is catalyzed by nitric oxide reductase (NOR); 2NO + 2e- + 2H+ → N2O + H2O. NOR from Paracoccus denitrificans is a member of the heme copper oxidase superfamily (HCuOs), where the mitochondrial cytochrome c oxidase is the classical example. NOR is situated in the cytoplasmic membrane and can, as a side reaction, catalyze the reduction of oxygen to water.

NORs have properties that make them divergent members of the HCuOs; the reactions they catalyze are not electrogenic and they do not pump protons. They also have five strictly conserved glutamates in their catalytic subunit (NorB) that are not conserved in the ‘classical’ HCuOs. It has been asked whether the protons used in the reaction really come from the periplasm and if so how do the protons proceed through the protein into the catalytic site?

In order to find out whether the protons are taken from the periplasm or the cytoplasm and in order to pinpoint the proton-route in NorB, we studied electron- and proton transfer during a single- as well as multiple turnovers, using time resolved optical spectroscopy. Wild type NOR and several variants of the five conserved glutamates were investigated in their solubilised form or/and reconstituted into vesicles.

The results demonstrate that protons needed for the reaction indeed are taken from the periplasm and that all but one of the conserved glutamates are crucial for the oxidative phase of the reaction that is limited by proton uptake to the active site.

In this thesis it is proposed, using a model of NorB, that two of the glutamates are located at the entrance of the proton pathway which also contains two of the other glutamates close to the active site.

Place, publisher, year, edition, pages
Stockholm: Institutionen för biokemi och biofysik, 2008. 113 p.
denitrification, nitric oxide reductase, heme copper oxidase superfamily, divergent member, proton transfer, electron transfer, single turnover, spectroscopy, periplasm, glutamate, proton pathway
National Category
Biochemistry and Molecular Biology
Research subject
urn:nbn:se:su:diva-8171 (URN)978-91-7155-740-7 (ISBN)
Public defence
2008-10-17, Magnélisalen, Kemiska övnigslaboratoriet, Svante Arrhenius väg 12 A, Stockholm, 10:00
Available from: 2008-09-25 Created: 2008-09-25 Last updated: 2015-09-24Bibliographically approved

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Flock, Ulrika
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