Linked Life Data

7867653

Source:http://linkedlifedata.com/resource/pubmed/id/7867653

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
3
pubmed:dateCreated
1995-3-28
pubmed:abstractText
The Escherichia coli quinol oxidase, cytochrome bo, is closely related to the cytochrome c oxidase, cytochrome aa3 in all aspects of its structure and function except for the replacement of the cytochrome-c-binding site and its attendant CuA prosthetic group with a quinone-binding site. The putative oxidation of quinol by ferrihaem (cytochrome b) at this site in sequential one-electron steps requires the stabilisation of semiquinone. We have observed, by electron paramagnetic resonance, the properties of a ubisemiquinone radical in appropriately poised samples of purified enzyme reconstituted with excess ubiquinone. The ubisemiquinone is highly stabilised with respect to free ubisemiquinone; significant free radical can be observed even at pH 7.0, while at pH 9.0 the stability constant is 5-10. The pH dependence of the stability constant indicates that the anionic form of the semiquinone predominates above pH 7.5. The two-electron couple has an Em7 of approximately 70 mV. Below pH 9, the pH dependence of the two-electron couple is -60mV/pH, indicative of a 2H+/2e- reaction. The line width of the EPR spectrum is approximately 0.9 mT, which is consistent with a ubisemiquinone anion. In comparison with other respiratory chain Q.- species that have been described, the relaxation rate in the presence of reduced haems appears comparable to magnetically isolated Q.- radicals. Partially resolved splittings of approximately 0.4 mT can be observed in the spectrum of Q.-bo (QH.bo).
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Feb
pubmed:issn
0014-2956
pubmed:author
pubmed:issnType
Print
pubmed:day
1
pubmed:volume
227
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
903-8
pubmed:dateRevised
2007-11-15
pubmed:meshHeading
pubmed:year
1995
pubmed:articleTitle
Studies on a stabilisation of ubisemiquinone by Escherichia coli quinol oxidase, cytochrome bo.
pubmed:affiliation
School of Biological and Medical Sciences, University of St. Andrews, Scotland.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, Non-P.H.S., Research Support, Non-U.S. Gov't