Linked Life Data

1327103

Source:http://linkedlifedata.com/resource/pubmed/id/1327103

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
36
pubmed:dateCreated
1992-10-26
pubmed:abstractText
Calcium binding to photosystem II slows NH2OH inhibition of O2 evolution; Mn2+ is retained by the O2-evolving complex [Mei, R., & Yocum, C. F. (1991) Biochemistry 30, 7836-7842]. This Ca(2+)-induced stability has been further characterized using the large reductant hydroquinone. Salt-washed photosystem II membranes reduced by hydroquinone in the presence of Ca2+ retain 80% of steady-state O2 evolution activity and contain about 2 Mn2+/reaction center that can be detected at room temperature by electron paramagnetic resonance. This Mn2+ produces a weak enhancement of H2O proton spin-lattice relaxation rates, cannot be easily extracted by a chelator, and is reincorporated into the O2-evolving complex upon illumination. A comparison of the properties of Ca(2+)-supplemented photosystem II samples reduced by hydroquinone or NH2OH alone or in sequence reveals the presence of a subpopulation of manganese atoms at the active site of H2O oxidation that is not accessible to facile hydroquinone reduction. At least one of these manganese atoms can be readily reduced by NH2OH following a noninhibitory hydroquinone reduction step. Under these conditions, about 3 Mn2+/reaction center are lost and O2 evolution activity is irreversibly inhibited. We interpret the existence of distinct sites of reductant action on manganese as further evidence that the Ca(2+)-binding site in photosystem II participates in regulation of the organization of manganese-binding ligands and the overall structure of the O2-evolving complex.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Sep
pubmed:issn
0006-2960
pubmed:author
pubmed:issnType
Print
pubmed:day
15
pubmed:volume
31
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
8449-54
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
1992
pubmed:articleTitle
Comparative properties of hydroquinone and hydroxylamine reduction of the Ca(2+)-stabilized O2-evolving complex of photosystem II: reductant-dependent Mn2+ formation and activity inhibition.
pubmed:affiliation
Department of Biology, University of Michigan, Ann Arbor 48109-1048.
pubmed:publicationType
Journal Article, Comparative Study, Research Support, U.S. Gov't, Non-P.H.S.