Transverse heterogeneity in lipid fluidity in spinach thylakoids,photosystem II preparations,and thylakoid galactolipid vesicles |
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Authors: | Charlene Waggoner Harold Aronson Iyoti More Steven P Berg |
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Institution: | (1) Department of Biological Sciences, University of Denver, 80208 Denver, Colorado, USA |
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Abstract: | We have used three doxyl stearic acid spin labels to study the transverse hetero-geneity in lipid fluidity in thylakoids, photosystem II (PS II) preparations, and thylakoid galactolipid vesicles. This comparative study shows that spin labels incorporated into the membrane of the PS II preparation experience far more immobilization than do the same spin labels incorporated into either thylakoids or vesicles prepared from the polar lipids extracted from thylakoids. The spin label immobilization found in the PS II preparation is manifest even near the center of the bilayer, where lipid mobility is normally at its maximum. Analysis of the lipid content of the PS II preparation, relative to chlorophyll, suggests that the PS II preparation may be lipid depleted. This lipid depletion could explain the results presented. However, electron microscopy Dunahay et al. (1984) Biochim. Biophys. Acta 764:179–193] has not indicated that major delipidation has occurred, and so it remains possible that the immobilization found in the PS II preparation is due primarily to the normal (but close) juxtaposition of adjacent PS II complexes and the cooperative immobilization of their surrounding lipids. Based on the results presented, we conclude that highly mobile lipids are not required for oxygen evolution, the primary photochemistry or the secondary reduction of exogenously added quinones. Unfortunately, the relationship between the plastoquinone pool and the fluidity of the membrane in the PS II preparation remains ambiguous.Abbreviations PS II
photosystem II
- SDSA
5-doxylstearic acid
- 12DSA
12-doxylstearic acid
- 16DSA
16-doxylstearic acid
- 7N14
2-heptyl-2-hexyl-5,5-dimethyloxazolidine-N-oxyl
- chromium oxalate
potassium trioxalatochromiate
- EPR
electron paramagnetic resonance
- Chl
chlorophyll
- MGDG
monogalactosyldiacylglycerol
- DGDG
digalactosyldiacylglycerol |
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Keywords: | Thylakoid membrane lipid fluidity photosynthesis photosystem II spin label electron paramagnetic resonance |
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