Proton translocation by the cytochrome bc(1) complexes of phototrophic bacteria: introducing the activated Q-cycle

DC FieldValueLanguage
dc.contributor.authorMulkidjanian, Armen Y.
dc.date.accessioned2021-12-23T16:11:48Z-
dc.date.available2021-12-23T16:11:48Z-
dc.date.issued2007
dc.identifier.issn1474905X
dc.identifier.urihttps://osnascholar.ub.uni-osnabrueck.de/handle/unios/9888-
dc.description.abstractThe cytochrome b(C1) complexes are proton-translocating, dimeric membrane ubiquinol: cytochrome c oxidoreductases that serve as ``hubs'' in the vast majority of electron transfer chains. After each ubiquinol molecule is oxidized in the catalytic center P at the positively charged membrane side, the two liberated electrons head out, according to the Mitchell's Q-cycle mechanism, to different acceptors. One is taken by the [2Fe-2S] iron-sulfur Rieske protein to be passed further to cytochrome c(1). The other electron goes across the membrane, via the low- and high-potential hemes of cytochrome b, to another ubiquinone-binding site N at the opposite membrane side. It has been assumed that two ubiquinol molecules have to be oxidized by center P to yield first a semiquinone in center N and then to reduce this semiquinone to ubiquinol. This review is focused on the operation of cytochrome b(C1) complexes in phototrophic purple bacteria. Their membranes provide a unique system where the generation of membrane voltage by light-driven, energy-converting enzymes can be traced via spectral shifts of native carotenoids and correlated with the electron and proton transfer reactions. An ``activated Q-cycle'' is proposed as a novel mechanism that is consistent with the available experimental data on the electron/proton coupling. Under physiological conditions, the dimeric cytochrome b(C1) complex is suggested to be continually primed by prompt oxidation of membrane ubiquinol via center N yielding a bound semiquinone in this center and a reduced, high-potential heme b in the other monomer of the enzyme. Then the oxidation of each ubiquinol molecule in center P is followed by ubiquinol formation in center N, proton translocation and generation of membrane voltage.
dc.language.isoen
dc.publisherSPRINGERNATURE
dc.relation.ispartofPHOTOCHEMICAL & PHOTOBIOLOGICAL SCIENCES
dc.subjectB-C2 OXIDOREDUCTASE
dc.subjectBiochemistry & Molecular Biology
dc.subjectBiophysics
dc.subjectChemistry
dc.subjectChemistry, Physical
dc.subjectCRYSTAL-STRUCTURE
dc.subjectIRON-SULFUR PROTEIN
dc.subjectOXIDOREDUCTASE COMPLEX
dc.subjectPHOTOSYNTHETIC ELECTRON-TRANSFER
dc.subjectRESPIRATORY-CHAIN
dc.subjectRHODOBACTER-CAPSULATUS
dc.subjectRHODOPSEUDOMONAS-SPHAEROIDES
dc.subjectSINGLE TURNOVER FLASH
dc.subjectUBIQUINOL-OXIDATION
dc.titleProton translocation by the cytochrome bc(1) complexes of phototrophic bacteria: introducing the activated Q-cycle
dc.typereview
dc.identifier.doi10.1039/b517522d
dc.identifier.isiISI:000243204700002
dc.description.volume6
dc.description.issue1
dc.description.startpage19
dc.description.endpage34
dc.contributor.orcid0000-0001-5844-3064
dc.contributor.researcheridAAH-3608-2021
dc.contributor.researcheridJ-8086-2013
dc.identifier.eissn14749092
dc.publisher.placeCAMPUS, 4 CRINAN ST, LONDON, N1 9XW, ENGLAND
dcterms.isPartOf.abbreviationPhotochem. Photobiol. Sci.
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