Multiple sites of retardation of electron transfer in Photosystem II after hydrolysis of phosphatidylglycerol |
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Authors: | Eun-Ha Kim Reza Razeghifard Jan M Anderson Wah Soon Chow |
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Institution: | (1) Photobioenergetics Group, Research School of Biological Sciences, Australian National University, GPO Box 475, Canberra, ACT, 2601, Australia;(2) Present address: Department of Anesthesiology, University of Michigan, 2215 Fuller Road, Ann Arbor, MI 48105, USA |
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Abstract: | Phosphatidylglycerol (PG), containing the unique fatty acid Δ3, trans-16:1-hexadecenoic acid, is a minor but ubiquitous lipid component of thylakoid membranes of chloroplasts and cyanobacteria.
We investigated its role in electron transfers and structural organization of Photosystem II (PSII) by treating Arabidopsis thaliana thylakoids with phospholipase A2 to decrease the PG content. Phospholipase A2 treatment of thylakoids (a) inhibited electron transfer from the primary quinone acceptor QA to the secondary quinone acceptor QB, (b) retarded electron transfer from the manganese cluster to the redox-active tyrosine Z, (c) decreased the extent of flash-induced
oxidation of tyrosine Z and dark-stable tyrosine D in parallel, and (d) inhibited PSII reaction centres such that electron
flow to silicomolybdate in continuous light was inhibited. In addition, phospholipase A2 treatment of thylakoids caused the partial dissociation of (a) PSII supercomplexes into PSII dimers that do not have the
complete light-harvesting complex of PSII (LHCII); (b) PSII dimers into monomers; and (c) trimers of LHCII into monomers.
Thus, removal of PG by phospholipase A2 brings about profound structural changes in PSII, leading to inhibition/retardation of electron transfer on the donor side,
in the reaction centre, and on the acceptor side. Our results broaden the simple view of the predominant effect being on the
QB-binding site. |
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Keywords: | Arabidopsis thaliana Phosphatidylglycerol Phospholipase A2 Photosystem II Thylakoid lipids Tyrosine Z |
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