Linked Life Data

1332780

Source:http://linkedlifedata.com/resource/pubmed/id/1332780

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
2
pubmed:dateCreated
1992-12-28
pubmed:abstractText
The reduction of the tetraheme cytochrome c3 (from Desulfovibrio vulgaris, strains Miyazaki F and Hildenbourough) by flavin semiquinone and reduced methyl viologen follows a monophasic kinetic profile, even though the four hemes do not have equivalent reduction potentials. Rate constants for reduction of the individual hemes are obtained subsequent to incrementally reducing the cytochrome by phototitration. The dependence of each rate constant on the reduction potential difference between the heme and the reductant can be described by outer sphere electron transfer theroy. Thus, the very low reduction potentials of the cytochrome c3 hemes compensate for the very large solvent accessibility of the hemes. The relative rate constants for electron transfer to the four hemes of cytochrome c3 are consistent with the assignments of reduction potential to hemes previously made by Park et al. (Park, J.-S., Kano, K., Niki, S. and Akutsu, H. (1991) FEBS Lett. 285, 149-151) using NMR techniques. The ionic strength dependence of the observed rate constant for reduction by the methyl viologen radical cation indicates that ionic strength substantially alters the structure and/or the heme reduction potentials of the cytochrome. This result is confirmed by reduction with a neutral flavin species (5-deazariboflavin semiquinone) in which the reactivity of the highest potential heme decreases and the reactivity of the lowest potential heme increases at high (500 mM) ionic strength, and by the sensitivity of heme methyl resonances to ionic strength as observed by 1H-NMR. These unusual ionic strength-dependent effects may be due to a combination of structural changes in the cytochrome and alterations of the electrostatic fields at elevated ionic strengths.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Dec
pubmed:issn
0006-3002
pubmed:author
pubmed:issnType
Print
pubmed:day
7
pubmed:volume
1140
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
144-56
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
1992
pubmed:articleTitle
Reduction kinetics of the four hemes of cytochrome c3 from Desulfovibrio vulgaris by flash photolysis.
pubmed:affiliation
Department of Biochemistry, University of Arizona, Tucson.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, Non-P.H.S., Research Support, Non-U.S. Gov't