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Microsecond Time-Resolved Absorption Spectroscopy Used to Study CO Compounds of Cytochrome bd from Escherichia coli

Cytochrome bd is a tri-heme (b (558), b (595), d) respiratory oxygen reductase that is found in many bacteria including pathogenic species. It couples the electron transfer from quinol to O(2) with generation of an electrochemical proton gradient. We examined photolysis and subsequent recombination...

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Autores principales: Siletsky, Sergey A., Zaspa, Andrey A., Poole, Robert K., Borisov, Vitaliy B.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Public Library of Science 2014
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3995794/
https://www.ncbi.nlm.nih.gov/pubmed/24755641
http://dx.doi.org/10.1371/journal.pone.0095617
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author Siletsky, Sergey A.
Zaspa, Andrey A.
Poole, Robert K.
Borisov, Vitaliy B.
author_facet Siletsky, Sergey A.
Zaspa, Andrey A.
Poole, Robert K.
Borisov, Vitaliy B.
author_sort Siletsky, Sergey A.
collection PubMed
description Cytochrome bd is a tri-heme (b (558), b (595), d) respiratory oxygen reductase that is found in many bacteria including pathogenic species. It couples the electron transfer from quinol to O(2) with generation of an electrochemical proton gradient. We examined photolysis and subsequent recombination of CO with isolated cytochrome bd from Escherichia coli in one-electron reduced (MV) and fully reduced (R) states by microsecond time-resolved absorption spectroscopy at 532-nm excitation. Both Soret and visible band regions were examined. CO photodissociation from MV enzyme possibly causes fast (τ<1.5 µs) electron transfer from heme d to heme b (595) in a small fraction of the protein, not reported earlier. Then the electron migrates to heme b (558) (τ∼16 µs). It returns from the b-hemes to heme d with τ∼180 µs. Unlike cytochrome bd in the R state, in MV enzyme the apparent contribution of absorbance changes associated with CO dissociation from heme d is small, if any. Photodissociation of CO from heme d in MV enzyme is suggested to be accompanied by the binding of an internal ligand (L) at the opposite side of the heme. CO recombines with heme d (τ∼16 µs) yielding a transient hexacoordinate state (CO-Fe(2+)-L). Then the ligand slowly (τ∼30 ms) dissociates from heme d. Recombination of CO with a reduced heme b in a fraction of the MV sample may also contribute to the 30-ms phase. In R enzyme, CO recombines to heme d (τ∼20 µs), some heme b (558) (τ∼0.2–3 ms), and finally migrates from heme d to heme b (595) (τ∼24 ms) in ∼5% of the enzyme population. Data are consistent with the recent nanosecond study of Rappaport et al. conducted on the membranes at 640-nm excitation but limited to the Soret band. The additional phases were revealed due to differences in excitation and other experimental conditions.
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spelling pubmed-39957942014-04-25 Microsecond Time-Resolved Absorption Spectroscopy Used to Study CO Compounds of Cytochrome bd from Escherichia coli Siletsky, Sergey A. Zaspa, Andrey A. Poole, Robert K. Borisov, Vitaliy B. PLoS One Research Article Cytochrome bd is a tri-heme (b (558), b (595), d) respiratory oxygen reductase that is found in many bacteria including pathogenic species. It couples the electron transfer from quinol to O(2) with generation of an electrochemical proton gradient. We examined photolysis and subsequent recombination of CO with isolated cytochrome bd from Escherichia coli in one-electron reduced (MV) and fully reduced (R) states by microsecond time-resolved absorption spectroscopy at 532-nm excitation. Both Soret and visible band regions were examined. CO photodissociation from MV enzyme possibly causes fast (τ<1.5 µs) electron transfer from heme d to heme b (595) in a small fraction of the protein, not reported earlier. Then the electron migrates to heme b (558) (τ∼16 µs). It returns from the b-hemes to heme d with τ∼180 µs. Unlike cytochrome bd in the R state, in MV enzyme the apparent contribution of absorbance changes associated with CO dissociation from heme d is small, if any. Photodissociation of CO from heme d in MV enzyme is suggested to be accompanied by the binding of an internal ligand (L) at the opposite side of the heme. CO recombines with heme d (τ∼16 µs) yielding a transient hexacoordinate state (CO-Fe(2+)-L). Then the ligand slowly (τ∼30 ms) dissociates from heme d. Recombination of CO with a reduced heme b in a fraction of the MV sample may also contribute to the 30-ms phase. In R enzyme, CO recombines to heme d (τ∼20 µs), some heme b (558) (τ∼0.2–3 ms), and finally migrates from heme d to heme b (595) (τ∼24 ms) in ∼5% of the enzyme population. Data are consistent with the recent nanosecond study of Rappaport et al. conducted on the membranes at 640-nm excitation but limited to the Soret band. The additional phases were revealed due to differences in excitation and other experimental conditions. Public Library of Science 2014-04-22 /pmc/articles/PMC3995794/ /pubmed/24755641 http://dx.doi.org/10.1371/journal.pone.0095617 Text en © 2014 Siletsky et al http://creativecommons.org/licenses/by/4.0/ This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are properly credited.
spellingShingle Research Article
Siletsky, Sergey A.
Zaspa, Andrey A.
Poole, Robert K.
Borisov, Vitaliy B.
Microsecond Time-Resolved Absorption Spectroscopy Used to Study CO Compounds of Cytochrome bd from Escherichia coli
title Microsecond Time-Resolved Absorption Spectroscopy Used to Study CO Compounds of Cytochrome bd from Escherichia coli
title_full Microsecond Time-Resolved Absorption Spectroscopy Used to Study CO Compounds of Cytochrome bd from Escherichia coli
title_fullStr Microsecond Time-Resolved Absorption Spectroscopy Used to Study CO Compounds of Cytochrome bd from Escherichia coli
title_full_unstemmed Microsecond Time-Resolved Absorption Spectroscopy Used to Study CO Compounds of Cytochrome bd from Escherichia coli
title_short Microsecond Time-Resolved Absorption Spectroscopy Used to Study CO Compounds of Cytochrome bd from Escherichia coli
title_sort microsecond time-resolved absorption spectroscopy used to study co compounds of cytochrome bd from escherichia coli
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3995794/
https://www.ncbi.nlm.nih.gov/pubmed/24755641
http://dx.doi.org/10.1371/journal.pone.0095617
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