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Proton transfer in uncoupled variants of cytochrome c oxidase
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 Organic Chemistry.
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
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(English)Manuscript (preprint) (Other academic)
Keywords [en]
electron transfer, proton transfer, cytochrome aa3, membrane protein, proton pumping, mechanism
National Category
Biochemistry and Molecular Biology
Research subject
Biochemistry
Identifiers
URN: urn:nbn:se:su:diva-173514OAI: oai:DiVA.org:su-173514DiVA, id: diva2:1354607
Available from: 2019-09-25 Created: 2019-09-25 Last updated: 2019-09-30Bibliographically approved
In thesis
1. Choreography of a proton pump: Studies of charge-transfer reactions in cytochrome c oxidase
Open this publication in new window or tab >>Choreography of a proton pump: Studies of charge-transfer reactions in cytochrome c oxidase
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In the last step of cellular respiration, electrons from metabolites are transferred to molecular oxygen, mediated by the enzyme complexes of the respiratory chain. Some of these enzyme complexes couple these redox reactions to formation of an electrochemical proton gradient across the cell membrane. The proton gradient is used e.g. by ATP synthase to drive synthesis of ATP. 

The terminal enzyme complex in the respiratory chain, cytochrome c oxidase (CytcO), catalyses reduction of O2 to water. In this process it contributes to maintaining the electrochemical proton gradient by two separate mechanisms: (i) by uptake of electrons and protons from the opposite sides of the membrane (for O2 reduction to water). (ii) by proton pumping across the membrane. Protons used in the O2 reduction, as well as protons that are pumped, are taken up through two different proton-uptake pathways, the D and the K pathways. In addition, a third proton-transfer pathway has been suggested for the mitochondrial CytcOs, namely the H pathway. So far, the molecular mechanism by which CytcO pumps protons has not been determined. 

In this work we have studied proton- and electron-transfer reactions in aa3-type CytcOs, with the aim of understanding the functional design of the proton-pumping machinery in CytcO. First, we studied structural variants of CytcO from the bacterium Rhodobacter (R.) sphaeroides, where an amino-acid at position 425, previously shown to undergo redox-induced conformational changes, was substituted. The results point to a link between redox-induced structural changes and intramolecular proton-transfer rates through the D pathway. Second, we studied the electron distribution in the “activated” oxidized (OH) state of CytcO, by using an electrostatic complex of CytcO and cytochrome c. We also investigated electron-transfer reactions linked to proton pumping in structural variants of CytcO from R. sphaeroides and the yeast Saccharomyces (S.) cerevisiae, with mutations in the proposed D and H proton-uptake pathways. The data indicate that the S. cerevisiae mitochondrial CytcO uses the D pathway for proton uptake and pumping as the R. sphaeroides CytcO. Lastly, we studied reactions linked to proton uptake and pumping in structural variants of CytcO from R. sphaeroides with alterations in both proton-uptake pathways. The data elucidated the mechanism of proton transfer and gating in CytcO.

Place, publisher, year, edition, pages
Stockholm: Department of Biochemistry and Biophysics, Stockholm University, 2019. p. 78
Keywords
heme-copper oxidase, cytochrome c oxidase, respiration, proton pump, electron transfer, proton transfer, proton-transfer pathway, midpoint potential, proton-pumping mechanism
National Category
Biochemistry and Molecular Biology
Research subject
Biochemistry
Identifiers
urn:nbn:se:su:diva-173568 (URN)978-91-7797-855-8 (ISBN)978-91-7797-856-5 (ISBN)
Public defence
2019-11-08, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 10:00 (English)
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Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.

Available from: 2019-10-16 Created: 2019-09-25 Last updated: 2019-10-08Bibliographically approved

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Vilhjálmsdóttir, JóhannaAlbertsson, IngridBlomberg, Margareta R. A.Ädelroth, PiaBrzezinski, Peter
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