1. Structural Entities Associated with Different Lipid Phases of Plant Thylakoid Membranes—Selective Susceptibilities to Different Lipases and Proteases.
- Author
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Dlouhý, Ondřej, Karlický, Václav, Javornik, Uroš, Kurasová, Irena, Zsiros, Ottó, Šket, Primož, Kanna, Sai Divya, Böde, Kinga, Večeřová, Kristýna, Urban, Otmar, Gasanoff, Edward S., Plavec, Janez, Špunda, Vladimír, Ughy, Bettina, and Garab, Győző
- Subjects
PLANT membranes ,PROTEOLYTIC enzymes ,PLANT lipids ,MEMBRANE fusion ,LIPASES ,PROTEINASES - Abstract
It is well established that plant thylakoid membranes (TMs), in addition to a bilayer, contain two isotropic lipid phases and an inverted hexagonal (H
II ) phase. To elucidate the origin of non-bilayer lipid phases, we recorded the31 P-NMR spectra of isolated spinach plastoglobuli and TMs and tested their susceptibilities to lipases and proteases; the structural and functional characteristics of TMs were monitored using biophysical techniques and CN-PAGE. Phospholipase-A1 gradually destroyed all31 P-NMR-detectable lipid phases of isolated TMs, but the weak signal of isolated plastoglobuli was not affected. Parallel with the destabilization of their lamellar phase, TMs lost their impermeability; other effects, mainly on Photosystem-II, lagged behind the destruction of the original phases. Wheat-germ lipase selectively eliminated the isotropic phases but exerted little or no effect on the structural and functional parameters of TMs—indicating that the isotropic phases are located outside the protein-rich regions and might be involved in membrane fusion. Trypsin and Proteinase K selectively suppressed the HII phase—suggesting that a large fraction of TM lipids encapsulate stroma-side proteins or polypeptides. We conclude that—in line with the Dynamic Exchange Model—the non-bilayer lipid phases of TMs are found in subdomains separated from but interconnected with the bilayer accommodating the main components of the photosynthetic machinery. [ABSTRACT FROM AUTHOR]- Published
- 2022
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