Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Timing of Electron and Proton Transfer in the ba(3) Cytochrome c Oxidase from Thermus thermophilus
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
Show others and affiliations
2012 (English)In: Biochemistry, ISSN 0006-2960, E-ISSN 1520-4995, Vol. 51, no 22, 4507-4517 p.Article in journal (Refereed) Published
Abstract [en]

Heme-copper oxidases are membrane-bound proteins that catalyze the reduction of O-2 to H2O, a highly exergonic reaction. Part of the free energy of this reaction is used for pumping of protons across the membrane. The ba(3) oxidase from Thermus thermophilus presumably uses a single proton pathway for the transfer of substrate protons used during O-2 reduction as well as for the transfer of the protons that are pumped across the membrane. The pumping stoichiometry (0.5 H+/electron) is lower than that of most other (mitochondrial-like) oxidases characterized to date (1 H+/electron). We studied the pH dependence and deuterium isotope effect of the kinetics of electron and proton transfer reactions in the ba3 oxidase. The results from these studies suggest that the movement of protons to the catalytic site and movement to a site located some distance from the catalytic site [proposed to be a proton-loading site (PLS) for pumped protons] are separated in time, which allows individual investigation of these reactions. A scenario in which the uptake and release of a pumped proton occurs upon every second transfer of an electron to the catalytic site would explain the decreased proton pumping stoichiometry compared to that of mitochondrial-like oxidases.

Place, publisher, year, edition, pages
2012. Vol. 51, no 22, 4507-4517 p.
National Category
Biochemistry and Molecular Biology
Research subject
Biochemistry
Identifiers
URN: urn:nbn:se:su:diva-79918DOI: 10.1021/bi300132tISI: 000304783200014OAI: oai:DiVA.org:su-79918DiVA: diva2:551609
Note

AuthorCount:5;

Available from: 2012-09-11 Created: 2012-09-11 Last updated: 2017-12-07Bibliographically approved
In thesis
1. Kinetics of proton and electron transfer in heme-copper oxidases
Open this publication in new window or tab >>Kinetics of proton and electron transfer in heme-copper oxidases
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Heme-copper oxidases are transmembrane proteins that are found in aerobic and anaerobic respiratory chains. During aerobic respiration, these enzymes reduce dioxygen to water. The energy released in the reaction is used to transport protons across a biological membrane. Stored as proton electrochemical gradient, the energy can be used to regenerate ATP. It is known that aa3 oxidases, which are the most common oxidases, transport pumped protons and protons used for the catalytic reaction using two proton pathways. However, the molecular mechanism of pumping is still being debated.

When oxygen is available in very small quantities, oxygen reductases with high affinity for oxygen are expressed by organisms like Thermus thermophilus. The proton pumping mechanism in the ba3 oxidase is slightly different from that of aa3 oxidases as this enzyme only uses a single proton uptake pathway. Here we analyzed the reaction mechanism of ba3 oxidase and found evidence that the first proton taken up by the four-electron reduced ba3 oxidase is transferred to a site distant from the catalytic site, the pump site, and that only every second proton taken up from solution is pumped. Data obtained from studies using site-directed mutagenesis and flow-flash spectroscopy suggest a probable location of the pump site.

Under anaerobic conditions, some organisms are able to generate a proton- motive force using nitrate and nitrite as electron acceptors. In this process, the cytotoxic reaction intermediate nitric oxide is produced. Nitric oxide reductase (NOR), a deviant heme-copper oxidase that reduces NO to the rather harmless N2O, does not pump any protons. The catalytic mechanism of nitric oxide reduction by NOR is very poorly understood.

Here we demonstrate that substrate inhibition, which occurs in NOR from Paracoccus denitrificans above 5 μM NO, can already be observed before the electrons from the low-spin hemes re-distribute to the active site. Furthermore, we found that a single specific proton pathway is used for proton-transfer leading from the periplasm to the active site. 

Place, publisher, year, edition, pages
Stockholm: Department of Biochemistry and Biophysics, Stockholm University, 2015. 64 p.
Keyword
Heme-copper oxidase, electron transfer, proton transfer, nitric oxide reductase, ba3 oxidase, flow-flash, laser-flash photolysis
National Category
Biochemistry and Molecular Biology
Research subject
Biochemistry
Identifiers
urn:nbn:se:su:diva-119996 (URN)978-91-7649-263-5 (ISBN)
Public defence
2015-11-23, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 10:00 (English)
Opponent
Supervisors
Available from: 2015-10-30 Created: 2015-08-31 Last updated: 2015-10-22Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full text

Search in DiVA

By author/editor
von Ballmoos, ChristophLachmann, PeterBrzezinski, Peter
By organisation
Department of Biochemistry and Biophysics
In the same journal
Biochemistry
Biochemistry and Molecular Biology

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 30 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf