Linked Life Data

9665705

Source:http://linkedlifedata.com/resource/pubmed/id/9665705

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
28
pubmed:dateCreated
1998-8-12
pubmed:abstractText
When unicellular algal cells are placed under anaerobic conditions, a large electrochemical gradient is built in darkness across the thylakoid membranes. We have estimated, in vivo, the amplitude of the Delta pH component of this transmembrane potential and shown that the Delta pH is twice as large as the Delta Psi. The amplitude of the Delta mu tildeH+ (approximately 110-140 mV) fits well with estimations based on the ATP/ADP ratio measured in green algae under the same conditions, suggesting that an equilibrium state is established across the thylakoid membrane. Therefore, under anaerobic dark incubation of algae, the electrochemical transmembrane potential is determined only by the cellular ATP content. The existence of this Delta mu tildeH+ is expected to result in a constitutive amount of activated CFo-CF1 ATPase, thereby facilitating ATP synthesis under low light intensity illumination. We report also on the effects of this dark-existing electrochemical gradient on the cytochrome b6f complex turnover kinetics. We show that they are largely slowed by the presence of this electrochemical transmembrane potential. The pH component is mainly responsible for the kinetic slowing down of cytochrome b6f complex turnover, despite the fact that electrogenicity is associated with the reactions taking place within this complex. Therefore, in vivo, owing to the low lumenal pH, the oxidation of plastoquinol at the Qo site is limiting the turnover of the cytochrome b6f complex in the presence of the Delta pH, while in its absence the oxidation rate of the b6 hemes becomes rate-limiting.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jul
pubmed:issn
0006-2960
pubmed:author
pubmed:issnType
Print
pubmed:day
14
pubmed:volume
37
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
9999-10005
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
1998
pubmed:articleTitle
In vivo characterization of the electrochemical proton gradient generated in darkness in green algae and its kinetic effects on cytochrome b6f turnover.
pubmed:affiliation
CNRS UPR 1261, Institut de Biologie Physico-Chimique, Paris, France. Finazzi@unimi.it
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't