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Action of K-crown ether on photosystem II electron transport: characterization of the site of action.
Indian J Biochem Biophys ; 1997 Jun; 34(3): 241-8
Article Dans Anglais | IMSEAR | ID: sea-28020
ABSTRACT
We have investigated the inhibitory effect of K-crown (18-crown-6 potassium picrate) on photosystem II (PSII)-enriched membrane fragments and O2-evolving core complexes. K-crown at 2-4 microM inhibits about half the control level of O2-evolution activity in both types of PSII samples. Oxygen-evolution studies demonstrated that the ether works by inactivating the centres and not by interfering with antenna function or energy transfer to the reaction centre. K-crown does not disrupt binding of the extrinsic proteins associated with O2 evolution nor complex with bound Ca2+ or Cl- cofactors, but rather it directly inhibits electron transfer after the tetrameric Mn cluster. Fluorescence studies on active and Tris-treated samples showed that K-crown does not prevent artificial donors from transferring electrons to PSII but like DCMU inhibits on the acceptor side after QA, the primary quinone acceptor. However, the ether is a leaky inhibitor and may also act as a weak donor when the Mn cluster is not present. Oxygen-production experiments using silicomolybdate as an artificial acceptor (which accepts from both pheophytin and QB in PSII membranes) demonstrated that the inhibition is at or near the DCMU site.
Sujets)
Texte intégral: Disponible Indice: IMSEAR (Asie du Sud-Est) Sujet Principal: Oxygène / Photosynthèse / Protéines végétales / Sites de fixation / Cinétique / Chlorophylle / Composés du silicium / Spinacia oleracea / Complexe protéique du centre réactionnel de la photosynthèse / Complexes collecteurs de lumière langue: Anglais Texte intégral: Indian J Biochem Biophys Année: 1997 Type: Article

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Texte intégral: Disponible Indice: IMSEAR (Asie du Sud-Est) Sujet Principal: Oxygène / Photosynthèse / Protéines végétales / Sites de fixation / Cinétique / Chlorophylle / Composés du silicium / Spinacia oleracea / Complexe protéique du centre réactionnel de la photosynthèse / Complexes collecteurs de lumière langue: Anglais Texte intégral: Indian J Biochem Biophys Année: 1997 Type: Article