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Titolo:
Influence of Ca2+ on the thylakoid lumen violaxanthin de-epoxidase activity through Ca2+ gating of H+ flux at the CFoH+ channel
Autore:
Pan, RS; Dilley, RA;
Indirizzi:
Purdue Univ, Dept Biol Sci, W Lafayette, IN 47907 USA Purdue Univ W Lafayette IN USA 47907 Biol Sci, W Lafayette, IN 47907 USA
Titolo Testata:
PHOTOSYNTHESIS RESEARCH
fascicolo: 2, volume: 65, anno: 2000,
pagine: 141 - 154
SICI:
0166-8595(2000)65:2<141:IOCOTT>2.0.ZU;2-G
Fonte:
ISI
Lingua:
ENG
Soggetto:
DELOCALIZED PROTON GRADIENTS; ISOLATED PEA-CHLOROPLASTS; ATP-SYNTHASE; XANTHOPHYLL CYCLE; INTACT CHLOROPLASTS; ZEAXANTHIN FORMATION; ELECTRON-TRANSPORT; LIGHT-INTENSITY; CALCIUM-BINDING; PHOTOSYSTEM-II;
Keywords:
Ca+ gating; proton channel; thylakoids; xanthophyll;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Agriculture,Biology & Environmental Sciences
Life Sciences
Citazioni:
66
Recensione:
Indirizzi per estratti:
Indirizzo: Dilley, RA Purdue Univ, Dept Biol Sci, W Lafayette, IN 47907 USA Purdue Univ W Lafayette IN USA 47907 W Lafayette, IN 47907 USA
Citazione:
R.S. Pan e R.A. Dilley, "Influence of Ca2+ on the thylakoid lumen violaxanthin de-epoxidase activity through Ca2+ gating of H+ flux at the CFoH+ channel", PHOTOSYN R, 65(2), 2000, pp. 141-154

Abstract

Part of the chloroplast photoprotection response to excess light absorption involves formation of zeaxanthin (and antheraxanthin) via the violaxanthin deepoxidase enzyme, the activity of which requires lumen acidity near or below pH 6.0. Clearly, the violaxanthin de-epoxidase activity is strongly regulated because at equivalent energization levels (including the parameters of H+ accumulation and ATP formation rates), there can be either low or high violaxanthin de-epoxidase enzyme activity. This work shows that the factor or factors responsible for regulating the violaxanthin deepoxidase correlate directly with those which regulate the expression of membrane-localized or delocalized proton gradient (Delta<(<mu>)over tilde>(H+)) energy coupling. The most clearly identified factor regulating switching between localized and delocalized energy coupling modes is Ca2+ binding to the lumen side of the thylakoid membrane; in particular, Ca2+ binding to the 8 kDA subunit III of the CFo H+ channel. The activity of violaxanthin deepoxidase in pea (Pisum sativa) and spinach ( Spinacea oleracea) thylakoids is shown hereto be strongly correlated with conditions known from previous work to displace Ca2+ from the CFo H+ channel and thus to modulate the extent of lumenal acidification while maintaining a fairly constant rate of ATP formation.

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Documento generato il 26/11/20 alle ore 11:35:38