Linked Life Data

8011646

Source:http://linkedlifedata.com/resource/pubmed/id/8011646

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
25
pubmed:dateCreated
1994-7-26
pubmed:abstractText
Asp235 in yeast cytochrome c peroxidase forms a hydrogen bond with His175, the proximal histidyl residue, that has been suggested to be important in determining the electronic properties of the heme iron and that may be involved in stabilizing the higher oxidation states of the peroxidase that form transiently during catalysis. The current study employs 1H and 15N-NMR spectroscopy to study the electronic properties of and the effects of pH on the active site of the Asp235Ala variant. This variant exhibits three spectroscopic species between pH 5 and 9: a high-spin species that forms at low pH and two low-spin species that form successively at higher pH. Nevertheless, the activity of the variant exhibits a pH dependence virtually identical to that of the wild-type protein, though the activity of the variant is 3 orders of magnitude lower at all values of pH between pH 5 and 8.5. These findings suggest that the spin state and coordination environment of the heme iron in cytochrome c peroxidase do not dictate the rate of substrate (cytochrome c) oxidation. Binding of cyanide to the variant enzyme results in formation of a single species as detected by NMR spectroscopy. Analysis of high-resolution 1D and 2D 1H-NMR and 15N-NMR spectra of the cyanide adduct has permitted characterization of the properties of this derivative and the strength of the proximal ligand bond to the heme iron. Disruption of the hydrogen bond between the proximal histidine and Asp235 that exists in the wild-type enzyme dramatically reduces the strength of the interaction between the proximal ligand and the iron; this effect combined with concurrent changes in the distal heme-binding pocket accounts for the increase in reduction potential reported for the Fe3+/Fe2+ couple. The catalytic consequences of the structural and electronic properties of the variant elucidated in this study are discussed.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jun
pubmed:issn
0006-2960
pubmed:author
pubmed:issnType
Print
pubmed:day
28
pubmed:volume
33
pubmed:geneSymbol
CcP
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
7819-29
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed-meshheading:8011646-Alanine, pubmed-meshheading:8011646-Aspartic Acid, pubmed-meshheading:8011646-Base Sequence, pubmed-meshheading:8011646-Binding Sites, pubmed-meshheading:8011646-Cytochrome-c Peroxidase, pubmed-meshheading:8011646-Electron Spin Resonance Spectroscopy, pubmed-meshheading:8011646-Heme, pubmed-meshheading:8011646-Histidine, pubmed-meshheading:8011646-Hydrogen Bonding, pubmed-meshheading:8011646-Hydrogen-Ion Concentration, pubmed-meshheading:8011646-Iron, pubmed-meshheading:8011646-Kinetics, pubmed-meshheading:8011646-Molecular Sequence Data, pubmed-meshheading:8011646-Mutagenesis, Site-Directed, pubmed-meshheading:8011646-Oligodeoxyribonucleotides, pubmed-meshheading:8011646-Recombinant Proteins, pubmed-meshheading:8011646-Spectrum Analysis, pubmed-meshheading:8011646-Structure-Activity Relationship, pubmed-meshheading:8011646-Temperature, pubmed-meshheading:8011646-Tryptophan
pubmed:year
1994
pubmed:articleTitle
Active site coordination chemistry of the cytochrome c peroxidase Asp235Ala variant: spectroscopic and functional characterization.
pubmed:affiliation
Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, Canada.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S., Research Support, Non-U.S. Gov't