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The mechanism for oxygen reduction in cytochrome c dependent nitric oxide reductase (cNOR) as obtained from a combination of theoretical and experimental results
Stockholm University, Faculty of Science, Department of Organic Chemistry.
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
Number of Authors: 22017 (English)In: Biochimica et Biophysica Acta - Bioenergetics, ISSN 0005-2728, E-ISSN 1879-2650, Vol. 1858, no 11, p. 884-894Article in journal (Refereed) Published
Abstract [en]

Bacterial NO-reductases (NOR) belong to the heme-copper oxidase (HCuO) superfamily, in which most members are O-2-reducing, proton-pumping enzymes. This study is one in a series aiming to elucidate the reaction mechanisms of the HCuOs, including the mechanisms for cellular energy conservation. One approach towards this goal is to compare the mechanisms for the different types of HCuOs, cytochrome c oxidase (CcO) and NOR, reducing the two substrates O-2 and NO. Specifically in this study, we describe the mechanism for oxygen reduction in cytochrome c dependent NOR (cNOR). Hybrid density functional calculations were performed on large cluster models of the cNOR binuclear active site. Our results are used, together with published experimental information, to construct a free energy profile for the entire catalytic cycle. Although the overall reaction is quite exergonic, we show that during the reduction of molecular oxygen in cNOR, two of the reduction steps are endergonic with high barriers for proton uptake, which is in contrast to oxygen reduction in CcO, where all reduction steps are exergonic. This difference between the two enzymes is suggested to be important for their differing capabilities for energy conservation. An additional result from this study is that at least three of the four reduction steps are initiated by proton transfer to the active site, which is in contrast to CcO, where electrons always arrive before the protons to the active site. The roles of the non-heme metal ion and the redox-active tyrosine in the active site are also discussed.

Place, publisher, year, edition, pages
2017. Vol. 1858, no 11, p. 884-894
Keywords [en]
Density functional theory, Energy profile, Cellular energy conservation, Electron transfer, Proton transfer, Non-heme iron
National Category
Biological Sciences Chemical Sciences
Identifiers
URN: urn:nbn:se:su:diva-148975DOI: 10.1016/j.bbabio.2017.08.005ISI: 000412611600002PubMedID: 28801051OAI: oai:DiVA.org:su-148975DiVA, id: diva2:1162808
Available from: 2017-12-05 Created: 2017-12-05 Last updated: 2017-12-05Bibliographically approved

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