Proton transfer in the quinol dependent nitric oxide reductase from geobacillus stearothermophilus during reduction of oxygen
2012 (English)In: Biochimica et Biophysica Acta - Bioenergetics, ISSN 0005-2728, E-ISSN 1879-2650, Vol. 1817, no 10, 1914-1920 p.Article in journal (Refereed) Published
Bacterial nitric oxide reductases (NOR) are integral membrane proteins that catalyse the reduction of nitric oxide to nitrous oxide, often as a step in the process of denitrification. Most functional data has been obtained with NORs that receive their electrons from a soluble cytochrome c in the periplasm and are hence termed cNOR. Very recently, the structure of a different type of NOR, the quinol-dependent (q)-NOR from the thermophilic bacterium Geobacillus stearothermophilus was solved to atomic resolution [Y. Matsumoto, T. Tosha, A.V. Pisliakov, T. Hino, H. Sugimoto, S. Nagano, Y. Sugita and Y. Shiro, Nat. Struct. Mol. Biol. 19 (2012) 238-246]. In this study, we have investigated the reaction between this gNOR and oxygen. Our results show that, like some cNORs, the C. stearothermophilus gNOR is capable of 02 reduction with a turnover of similar to 3 electrons s(-1) at 40 degrees C. Furthermore, using the so-called flow-flash technique, we show that the fully reduced (with three available electrons) gNOR reacts with oxygen in a reaction with a time constant of 1.8 ms that oxidises the low-spin heme b. This reaction is coupled to proton uptake from solution and presumably forms a ferryl intermediate at the active site. The pH dependence of the reaction is markedly different from a corresponding reaction in cNOR from Paracoccus denitrificans, indicating that possibly the proton uptake mechanism and/or pathway differs between gNOR and cNOR. This study furthermore forms the basis for investigation of the proton transfer pathway in gNOR using both variants with putative proton transfer elements modified and measurements of the vectorial nature of the proton transfer. This article is part of a Special Issue entitled: 17th European Bioenergetics Conference (EBEC 2012).
Place, publisher, year, edition, pages
2012. Vol. 1817, no 10, 1914-1920 p.
Heme-copper oxidase, Proton transfer pathway, Non-heme iron, Flow-flash, Carbon monoxide
Biochemistry and Molecular Biology Biophysics
IdentifiersURN: urn:nbn:se:su:diva-81832DOI: 10.1016/j.bbabio.2012.04.007ISI: 000307918200028OAI: oai:DiVA.org:su-81832DiVA: diva2:565372