Role of isotropic lipid phase in the fusion of photosystem II membranes

• DOI: 10.1007/s11120-024-01097-3
• Publication Date: 2024-04-25T10:02:14Z
• Authors: Kinga Böde; Uroš Javornik; Ondřej Dlouhý; Ottó Zsíros; Avratanu Biswas; Ildikó Domonkos; Primož Šket; Václav Karlický; Bettina Ughy; Petar H. Lambrev; Vladimír Špunda; Janez Plavec; Győző Garab
• Keywords: lipaza; 0301 basic medicine; 570; Magnetic Resonance Spectroscopy; violaxanthin de-epoxidase; Thylakoids; Membrane Fusion; higher-plants; 03 medical and health sciences; biokemija, NMR, spektroskopija, lipaza, pšenični kalčki; QK10 Plant physiology / növényélettan; Wheat germ lipase; QH301 Biology / biológia; biokemija; nonbilayer lipids; model; Research; a/b protein complex; Membrane fusion, non-bilayer lipids; spektroskopija; Photosystem II Protein Complex; P-31-NMR spectroscopy, BBY membrane; thylakoid membrane; dynamics; organization; Lipids; NMR; xanthophyll cycle enzyme; info:eu-repo/classification/udc/577; chlorophyll-a; Linear dichroism spectroscopy; pšenični kalčki

AbstractIt has been thoroughly documented, by using 31P-NMR spectroscopy, that plant thylakoid membranes (TMs), in addition to the bilayer (or lamellar, L) phase, contain at least two isotropic (I) lipid phases and an inverted hexagonal (HII) phase. However, our knowledge concerning the structural and functional roles of the non-bilayer phases is still rudimentary. The objective of the present study is to elucidate the origin of I phases which have been hypothesized to arise, in part, from the fusion of TMs (Garab et al. 2022 Progr Lipid Res 101,163). We take advantage of the selectivity of wheat germ lipase (WGL) in eliminating the I phases of TMs (Dlouhý et al. 2022 Cells 11: 2681), and the tendency of the so-called BBY particles, stacked photosystem II (PSII) enriched membrane pairs of 300–500 nm in diameter, to form large laterally fused sheets (Dunahay et al. 1984 BBA 764: 179). Our 31P-NMR spectroscopy data show that BBY membranes contain L and I phases. Similar to TMs, WGL selectively eliminated the I phases, which at the same time exerted no effect on the molecular organization and functional activity of PSII membranes. As revealed by sucrose-density centrifugation, magnetic linear dichroism spectroscopy and scanning electron microscopy, WGL disassembled the large laterally fused sheets. These data provide direct experimental evidence on the involvement of I phase(s) in the fusion of stacked PSII membrane pairs, and strongly suggest the role of non-bilayer lipids in the self-assembly of the TM system.