Linked Life Data

10220343

Source:http://linkedlifedata.com/resource/pubmed/id/10220343

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
17
pubmed:dateCreated
1999-5-14
pubmed:abstractText
Mitochondrial cytochromes c from spinach, cucumber, and sweet potato have been investigated through direct electrochemical measurements and electronic and 1H NMR spectroscopies, under conditions of varying temperature and pH. The solution behaviors of these plant cytochromes closely resemble, but do not fully reproduce, those of homologous eukaryotic species. The reduction potentials (E0') at pH 7 and 25 degrees C are +0.268 V (spinach), +0.271 V (cucumber), and +0.274 V (sweet potato) vs SHE. Three acid-base equilibria have been determined for the oxidized proteins with apparent pKa values of 2.5, 4.8, and 8.3-8.9, which are related to disruption of axial heme ligation, deprotonation of the solvent-exposed heme propionate-7 and replacement of the methionine axially bound to the heme iron with a stronger ligand, respectively. The most significant peculiarities with respect to the mammalian analogues include: (i) less negative reduction enthalpies and entropies (Delta S0'rc and Delta H0'rc) for the various protein conformers [low- and high-T native (N1 and N2) and alkaline (A)], whose effects at pH 7 and 25 degrees C largely compensate to produce E degrees ' values very similar to those of the mammalian proteins; (ii) the N1 --> N2 transition that occurs at a lower temperature (e.g., 30-35 degrees C vs 50 degrees C at pH 7. 5) and at a lower pH (7 vs 7.5); and (iii) a more pronounced temperature-induced decrease in the pKa for the alkaline transition which allows observation of the alkaline conformer(s) at pH values as low as 7 upon increasing the temperature above 40 degrees C. Regarding the pH and the temperature ranges of existence of the various protein conformers, these plant cytochromes c are closer to bacterial cytochromes c2.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Apr
pubmed:issn
0006-2960
pubmed:author
pubmed:issnType
Print
pubmed:day
27
pubmed:volume
38
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
5553-62
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
1999
pubmed:articleTitle
Redox chemistry and acid-base equilibria of mitochondrial plant cytochromes c.
pubmed:affiliation
Department of Chemistry, University of Modena and Reggio Emilia, Italy.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't