Source:http://linkedlifedata.com/resource/pubmed/id/10801789
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rdf:type | |
lifeskim:mentions |
umls-concept:C0013846,
umls-concept:C0022702,
umls-concept:C0029144,
umls-concept:C0031862,
umls-concept:C0053241,
umls-concept:C0205145,
umls-concept:C0205349,
umls-concept:C0271510,
umls-concept:C0449851,
umls-concept:C0596988,
umls-concept:C0599131,
umls-concept:C1517294,
umls-concept:C1547239,
umls-concept:C1721101,
umls-concept:C2603343
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pubmed:issue |
31
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pubmed:dateCreated |
2000-9-7
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pubmed:abstractText |
Interruption of the menA or menB gene in Synechocystis sp. PCC 6803 results in the incorporation of a foreign quinone, termed Q, into the A(1) site of photosystem I with a number of experimental indicators identifying Q as plastoquinone-9. A global multiexponential analysis of time-resolved optical spectra in the blue region shows the following three kinetic components: 1) a 3-ms lifetime in the absence of methyl viologen that represents charge recombination between P700(+) and an FeS(-) cluster; 2) a 750-microseconds lifetime that represents electron donation from an FeS(-) cluster to methyl viologen; and 3) an approximately 15-microseconds lifetime that represents an electrochromic shift of a carotenoid pigment. Room temperature direct detection transient EPR studies of forward electron transfer show a spectrum of P700(+) Q(-) during the lifetime of the spin polarization and give no evidence of a significant population of P700(+) FeS(-) for t </= 2-3 microseconds. The UV difference spectrum measured 5 microseconds after a flash shows a maximum at 315 nm, a crossover at 280 nm, and a minimum at 255 nm as well as a shoulder at 290-295 nm, all of which are characteristic of the plastoquinone-9 anion radical. Kinetic measurements that monitor Q at 315 nm show a major phase of forward electron transfer to the FeS clusters with a lifetime of approximately 15 microseconds, which matches the electrochromic shift at 485 nm of the carotenoid, as well as an minor phase with a lifetime of approximately 250 microseconds. Electrometric measurements show similar biphasic kinetics. The slower kinetic phase can be detected using time-resolved EPR spectroscopy and has a spectrum characteristic of a semiquinone anion radical. We estimate the redox potential of plastoquinone-9 in the A(1) site to be more oxidizing than phylloquinone so that electron transfer from Q(-) to F(X) is thermodynamically unfavorable in the menA and menB mutants.
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pubmed:language |
eng
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pubmed:journal | |
pubmed:citationSubset |
IM
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pubmed:chemical |
http://linkedlifedata.com/resource/pubmed/chemical/Alkyl and Aryl Transferases,
http://linkedlifedata.com/resource/pubmed/chemical/Chlorophyll,
http://linkedlifedata.com/resource/pubmed/chemical/Free Radicals,
http://linkedlifedata.com/resource/pubmed/chemical/Photosynthetic Reaction Center...,
http://linkedlifedata.com/resource/pubmed/chemical/Plastoquinone,
http://linkedlifedata.com/resource/pubmed/chemical/Vitamin K 1,
http://linkedlifedata.com/resource/pubmed/chemical/chlorophyll P 700,
http://linkedlifedata.com/resource/pubmed/chemical/phytyltransferase
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pubmed:status |
MEDLINE
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pubmed:month |
Aug
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pubmed:issn |
0021-9258
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pubmed:author | |
pubmed:issnType |
Print
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pubmed:day |
4
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pubmed:volume |
275
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pubmed:owner |
NLM
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pubmed:authorsComplete |
Y
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pubmed:pagination |
23429-38
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pubmed:dateRevised |
2006-11-15
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pubmed:meshHeading |
pubmed-meshheading:10801789-Alkyl and Aryl Transferases,
pubmed-meshheading:10801789-Chlorophyll,
pubmed-meshheading:10801789-Cyanobacteria,
pubmed-meshheading:10801789-Electron Spin Resonance Spectroscopy,
pubmed-meshheading:10801789-Electron Transport,
pubmed-meshheading:10801789-Free Radicals,
pubmed-meshheading:10801789-Kinetics,
pubmed-meshheading:10801789-Mutation,
pubmed-meshheading:10801789-Oxidation-Reduction,
pubmed-meshheading:10801789-Photosynthetic Reaction Center Complex Proteins,
pubmed-meshheading:10801789-Plastoquinone,
pubmed-meshheading:10801789-Potentiometry,
pubmed-meshheading:10801789-Spectrophotometry,
pubmed-meshheading:10801789-Thermodynamics,
pubmed-meshheading:10801789-Vitamin K 1
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pubmed:year |
2000
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pubmed:articleTitle |
Recruitment of a foreign quinone into the A1 site of photosystem I. Altered kinetics of electron transfer in phylloquinone biosynthetic pathway mutants studied by time-resolved optical, EPR, and electrometric techniques.
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pubmed:affiliation |
A. N. Belozersky Institute of Physicochemical Biology, Moscow State University, 119899 Moscow, Russia.
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pubmed:publicationType |
Journal Article,
Research Support, U.S. Gov't, Non-P.H.S.,
Research Support, Non-U.S. Gov't
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