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Active Site Midpoint Potentials in Different Cytochrome c Oxidase Families: A Computational Comparison
Stockholm University, Faculty of Science, Department of Organic Chemistry.ORCID iD: 0000-0003-0702-7831
Number of Authors: 12019 (English)In: Biochemistry, ISSN 0006-2960, E-ISSN 1520-4995, Vol. 58, no 15, p. 2028-2038Article in journal (Refereed) Published
Abstract [en]

Cytochrome c oxidase (CcO) is the terminal enzyme in the respiratory electron transport chain, reducing molecular oxygen to water. The binuclear active site in CcO comprises a high-spin heme associated with a Cu-B complex and a redox active tyrosine. The electron transport in the respiratory chain is driven by increasing midpoint potentials of the involved cofactors, resulting in a release of free energy, which is stored by coupling the electron transfer to proton translocation across a membrane, building up an electrochemical gradient. In this context, the midpoint potentials of the active site cofactors in the CcOs are of special interest, since they determine the driving forces for the individual oxygen reduction steps and thereby affect the efficiency of the proton pumping. It has been difficult to obtain useful information on some of these midpoint potentials from experiments. However, since each of the reduction steps in the catalytic cycle of oxygen reduction to water corresponds to the formation of an O-H bond, they can be calculated with a reasonably high accuracy using quantum chemical methods. From the calculated O-H bond strengths, the proton-coupled midpoint potentials of the active site cofactors can be estimated. Using models representing the different families of CcO's (A, B, and C), the calculations give midpoint potentials that should be relevant during catalytic turnover. The calculations also suggest possible explanations for why some experimentally measured potentials deviate significantly from the calculated ones, i.e., for Cu-B in all oxidase families, and for heme b(3) in the C family.

Place, publisher, year, edition, pages
2019. Vol. 58, no 15, p. 2028-2038
National Category
Organic Chemistry
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URN: urn:nbn:se:su:diva-169127DOI: 10.1021/acs.biochem.9b00093ISI: 000465189700010PubMedID: 30892888OAI: oai:DiVA.org:su-169127DiVA, id: diva2:1319382
Available from: 2019-05-31 Created: 2019-05-31 Last updated: 2019-05-31Bibliographically approved

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