Linked Life Data

18215069

Source:http://linkedlifedata.com/resource/pubmed/id/18215069

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
8
pubmed:dateCreated
2008-2-19
pubmed:abstractText
The mitochondrial bc1 complex catalyzes the oxidation of ubiquinol and the reduction of cytochrome (cyt) c coupled to a vectorial translocation of protons across the membrane. On the basis of the three-dimensional structures of the bc1 complex in the presence of the inhibitor stigmatellin, it was assumed that the substrate quinol binding involves the cyt b glutamate residue E272 and the histidine 181 on the Rieske protein. Although extensive mutagenesis of glutamate E272 has been carried out, different experimental results were recently obtained, and different conclusions were drawn to explain its role in the bifurcated electron/proton transfer at the QO site. This residue is not totally conserved during evolution. We show in this study that replacement of E272 with apolar residues proline and valine naturally present in some organisms did not abolish the bc1 activity, although it slowed down the kinetics of electron transfer. The Km value for the binding of the substrate quinol was not modified, and the EPR data showed that the quinone/quinol binding still occurred in the mutants. Binding of stigmatellin was retained; however, mutations E272P,V induced resistance toward the QO site inhibitor myxothiazol. The pH dependence of the bc1 activity was not modified in the absence of the glutamate E272. Our results suggest that this residue may not be involved in direct substrate binding or in its direct deprotonation. Revertants were selected from the respiratory deficient mutant E272P. The observed suppressor mutations introduced polar residues serine and threonine at position 272. The data lead us to suggest that E272 may be involved in a later step on the proton exit pathway via the interaction with a water molecule.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Feb
pubmed:issn
0006-2960
pubmed:author
pubmed:issnType
Print
pubmed:day
26
pubmed:volume
47
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
2357-68
pubmed:meshHeading
pubmed-meshheading:18215069-Amino Acid Sequence, pubmed-meshheading:18215069-Binding Sites, pubmed-meshheading:18215069-Cell Respiration, pubmed-meshheading:18215069-Conserved Sequence, pubmed-meshheading:18215069-Cytochromes b, pubmed-meshheading:18215069-Cytochromes c1, pubmed-meshheading:18215069-Electron Transport, pubmed-meshheading:18215069-Glutamic Acid, pubmed-meshheading:18215069-Hydrogen-Ion Concentration, pubmed-meshheading:18215069-Hydroquinones, pubmed-meshheading:18215069-Models, Molecular, pubmed-meshheading:18215069-Molecular Sequence Data, pubmed-meshheading:18215069-Multiprotein Complexes, pubmed-meshheading:18215069-Mutagenesis, Site-Directed, pubmed-meshheading:18215069-Mutant Proteins, pubmed-meshheading:18215069-Oxidation-Reduction, pubmed-meshheading:18215069-Protein Binding, pubmed-meshheading:18215069-Protons, pubmed-meshheading:18215069-Saccharomyces cerevisiae, pubmed-meshheading:18215069-Sequence Homology, Amino Acid, pubmed-meshheading:18215069-Ubiquinone
pubmed:year
2008
pubmed:articleTitle
Is cytochrome b glutamic acid 272 a quinol binding residue in the bc1 complex of Saccharomyces cerevisiae?
pubmed:affiliation
Laboratoire de Bioénergétique et Ingénierie des Protéines, CNRS, 31 Chemin Joseph Aiguier, 13402 Marseille cedex 20, France.
pubmed:publicationType
Journal Article