The Protonation State of a Heme Propionate Controls Electron Transfer in Cytochrome c Oxidase
| ISSN: | 1520-4995 0006-2960 |
|---|---|
| DOI: | 10.1021/bi0502745 |
| Přístupová URL adresa: | https://explore.openaire.eu/search/publication?articleId=doi_dedup___::0fa0294cf4a1066f24ebf5cb13808686 https://doi.org/10.1021/bi0502745 |
| Přírůstkové číslo: | edsair.doi.dedup.....0fa0294cf4a1066f24ebf5cb13808686 |
| Autor: | Gisela Brändén, Magnus Brändén, Peter Brzezinski, Denise A. Mills, Bryan Schmidt, Shelagh Ferguson-Miller |
| Rok vydání: | 2005 |
| Předmět: |
Stereochemistry
Protonation Heme Rhodobacter sphaeroides macromolecular substances Photochemistry Biochemistry Electron Transport Electron Transport Complex IV chemistry.chemical_compound Electron transfer Catalytic Domain Animals Horses Photolysis biology Cytochrome c Hydrogen-Ion Concentration Proton Pumps Electron transport chain Proton pump Solutions Heme A Models Chemical chemistry biology.protein Thermodynamics Propionates Protons Oxidation-Reduction |
| Zdroj: | Biochemistry. 44:10466-10474 |
| ISSN: | 1520-4995 0006-2960 |
| DOI: | 10.1021/bi0502745 |
| Popis: | In cytochrome c oxidase (CcO), exergonic electron transfer reactions from cytochrome c to oxygen drive proton pumping across the membrane. Elucidation of the proton pumping mechanism requires identification of the molecular components involved in the proton transfer reactions and investigation of the coupling between internal electron and proton transfer reactions in CcO. While the proton-input trajectory in CcO is relatively well characterized, the components of the output pathway have not been identified in detail. In this study, we have investigated the pH dependence of electron transfer reactions that are linked to proton translocation in a structural variant of CcO in which Arg481, which interacts with the heme D-ring propionates in a proposed proton output pathway, was replaced with Lys (RK481 CcO). The results show that in RK481 CcO the midpoint potentials of hemes a and a(3) were lowered by approximately 40 and approximately 15 mV, respectively, which stabilizes the reduced state of Cu(A) during reaction of the reduced CcO with O(2). In addition, while the pH dependence of the F --> O rate in wild-type CcO is determined by the protonation state of two protonatable groups with pK(a) values of 6.3 and 9.4, only the high-pK(a) group influences this rate in RK481 CcO. The results indicate that the protonation state of the Arg481 heme a(3) D-ring propionate cluster having a pK(a) of approximately 6.3 modulates the rate of internal electron transfer and may act as an acceptor of pumped protons. |
| Databáze: | OpenAIRE |
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