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Blomberg MRA, Ädelroth P. Mechanisms for enzymatic reduction of nitric oxide to nitrous oxide - A comparison between nitric oxide reductase and cytochrome c oxidase. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2018; 1859:1223-1234. [PMID: 30248312 DOI: 10.1016/j.bbabio.2018.09.368] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/03/2018] [Revised: 08/23/2018] [Accepted: 09/17/2018] [Indexed: 12/22/2022]
Abstract
Cytochrome c oxidases (CcO) reduce O2 to H2O in the respiratory chain of mitochondria and many aerobic bacteria. In addition, some species of CcO can also reduce NO to N2O and water while others cannot. Here, the mechanism for NO-reduction in CcO is investigated using quantum mechanical calculations. Comparison is made to the corresponding reaction in a "true" cytochrome c-dependent NO reductase (cNOR). The calculations show that in cNOR, where the reduction potentials are low, the toxic NO molecules are rapidly reduced, while the higher reduction potentials in CcO lead to a slower or even impossible reaction, consistent with experimental observations. In both enzymes the reaction is initiated by addition of two NO molecules to the reduced active site, forming a hyponitrite intermediate. In cNOR, N2O can then be formed using only the active-site electrons. In contrast, in CcO, one proton-coupled reduction step most likely has to occur before N2O can be formed, and furthermore, proton transfer is most likely rate-limiting. This can explain why different CcO species with the same heme a3-Cu active site differ with respect to NO reduction efficiency, since they have a varying number and/or properties of proton channels. Finally, the calculations also indicate that a conserved active site valine plays a role in reducing the rate of NO reduction in CcO.
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Affiliation(s)
- Margareta R A Blomberg
- Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, Stockholm SE-106 91, Sweden.
| | - Pia Ädelroth
- Department of Biochemistry and Biophysics, Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
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Andersson R, Safari C, Dods R, Nango E, Tanaka R, Yamashita A, Nakane T, Tono K, Joti Y, Båth P, Dunevall E, Bosman R, Nureki O, Iwata S, Neutze R, Brändén G. Serial femtosecond crystallography structure of cytochrome c oxidase at room temperature. Sci Rep 2017; 7:4518. [PMID: 28674417 PMCID: PMC5495810 DOI: 10.1038/s41598-017-04817-z] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2017] [Accepted: 05/19/2017] [Indexed: 11/11/2022] Open
Abstract
Cytochrome c oxidase catalyses the reduction of molecular oxygen to water while the energy released in this process is used to pump protons across a biological membrane. Although an extremely well-studied biological system, the molecular mechanism of proton pumping by cytochrome c oxidase is still not understood. Here we report a method to produce large quantities of highly diffracting microcrystals of ba3-type cytochrome c oxidase from Thermus thermophilus suitable for serial femtosecond crystallography. The room-temperature structure of cytochrome c oxidase is solved to 2.3 Å resolution from data collected at an X-ray Free Electron Laser. We find overall agreement with earlier X-ray structures solved from diffraction data collected at cryogenic temperature. Previous structures solved from synchrotron radiation data, however, have shown conflicting results regarding the identity of the active-site ligand. Our room-temperature structure, which is free from the effects of radiation damage, reveals that a single-oxygen species in the form of a water molecule or hydroxide ion is bound in the active site. Structural differences between the ba3-type and aa3-type cytochrome c oxidases around the proton-loading site are also described.
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Affiliation(s)
- Rebecka Andersson
- Department of Chemistry and Molecular Biology, University of Gothenburg, Box 462, SE-40530, Gothenburg, Sweden
| | - Cecilia Safari
- Department of Chemistry and Molecular Biology, University of Gothenburg, Box 462, SE-40530, Gothenburg, Sweden
| | - Robert Dods
- Department of Chemistry and Molecular Biology, University of Gothenburg, Box 462, SE-40530, Gothenburg, Sweden
| | - Eriko Nango
- RIKEN Spring-8 Center, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo, 679-5148, Japan.,Department of Cell Biology, Graduate School of Medicine, Kyoto University, Yoshidakonoe-cho, Sakyo-ku, Kyoto, 606-8501, Japan
| | - Rie Tanaka
- RIKEN Spring-8 Center, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo, 679-5148, Japan
| | - Ayumi Yamashita
- RIKEN Spring-8 Center, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo, 679-5148, Japan
| | - Takanori Nakane
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo, 113-0032, Japan
| | - Kensuke Tono
- Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo, 679-5198, Japan
| | - Yasumasa Joti
- Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo, 679-5198, Japan
| | - Petra Båth
- Department of Chemistry and Molecular Biology, University of Gothenburg, Box 462, SE-40530, Gothenburg, Sweden
| | - Elin Dunevall
- Department of Chemistry and Molecular Biology, University of Gothenburg, Box 462, SE-40530, Gothenburg, Sweden
| | - Robert Bosman
- Department of Chemistry and Molecular Biology, University of Gothenburg, Box 462, SE-40530, Gothenburg, Sweden
| | - Osamu Nureki
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo, 113-0032, Japan
| | - So Iwata
- RIKEN Spring-8 Center, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo, 679-5148, Japan.,Department of Cell Biology, Graduate School of Medicine, Kyoto University, Yoshidakonoe-cho, Sakyo-ku, Kyoto, 606-8501, Japan
| | - Richard Neutze
- Department of Chemistry and Molecular Biology, University of Gothenburg, Box 462, SE-40530, Gothenburg, Sweden
| | - Gisela Brändén
- Department of Chemistry and Molecular Biology, University of Gothenburg, Box 462, SE-40530, Gothenburg, Sweden.
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