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Investigation of the electron transfer site of p-benzoquinone in isolated photosystem II particles and thylakoid membranes using α- and β-cyclodextrins

Paper ID Volume ID Publish Year Pages File Format Full-Text
31186 44564 2006 7 PDF Available
Title
Investigation of the electron transfer site of p-benzoquinone in isolated photosystem II particles and thylakoid membranes using α- and β-cyclodextrins
Abstract

The electron transfer sites of p-benzoquinone (pBQ) and 2,6-dichloro-p-benzoquinone (DCBQ) were investigated in thylakoid membranes and isolated photosystem II (PSII) particles from barley (Hordeum vulgare) using α- and β-cyclodextrins (CD) at concentrations up to 16 mM. In CD-treated thylakoid membranes incubated with DCBQ the electron transport through PSII, estimated as oxygen evolution (OE), is largely enhanced according to a S-shaped (sigmoidal) dose–response curve displaying a sharp inflection point, or transition. The maxima percent OE enhancement at cyclodextrin concentrations above 14 mM are about 100% (α-CD) and 190% (β-CD). On the contrary, in thylakoid membrane preparations incubated with pBQ as electron acceptor one observes an OE inhibition of about 30% which might result from the depletion of the thylakoid membrane of its plastoquinone content. It was also found that in isolated PSII particles incubated with either pBQ or DCBQ the cyclodextrins induce only a small OE enhancement. Moreover, the observation in CD-treated thylakoid membranes incubated with pBQ of a residual, non-inhibited oxygen-evolving activity of about 70% puts a twofold question. That is, either the plastoquinone depletion was not complete, or, pBQ binds to electron acceptor sites of different nature. From this and data published in the literature, it is concluded that in the thylakoid membrane (i) DCBQ binds to QB, as is generally accepted, and (ii) pBQ binds to the plastoquinol molecules in the PQ pool and most likely also to QB, thereby in accord with Satoh et al.’s model [K. Satoh, M. Ohhashi, Y. Kashino, H. Koike, Plant Cell Physiol. 36 (1995) 597–605]. An attractive alternative hypothesis is the direct interaction of pBQ with the non-haem Fe2+ between QA and QB.

Keywords
Benzoquinones; Cyclodextrins; Electron transport; Oxygen evolution; Photosystem II; PSII particles; Thylakoid membranes
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Investigation of the electron transfer site of p-benzoquinone in isolated photosystem II particles and thylakoid membranes using α- and β-cyclodextrins
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Publisher
Database: Elsevier - ScienceDirect
Journal: Journal of Photochemistry and Photobiology B: Biology - Volume 85, Issue 3, 1 December 2006, Pages 177–183
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us