Fehér Bence, Nagy Gergely, Garab Győző
Nanobiophysics Research Group, HUN-REN Office for Supported Research Groups, Budapest, 1094, Hungary.
Institute of Biophysics and Radiation Biology, Semmelweis University, Budapest, 1094, Hungary.
Photosynth Res. 2025 Jun 11;163(3):36. doi: 10.1007/s11120-025-01156-3.
In oxygenic photosynthetic organisms, the light reactions are performed by protein complexes embedded in the lipid bilayer of thylakoid membranes (TMs). The organization of the bulk lipid molecules into bilayer structures provide optimal conditions for the build-up of the proton motive force (pmf) and its utilization for ATP synthesis. However, the lipid composition of TMs is dominated by the non-bilayer lipid species monogalactosyl diacylglycerol (MGDG), and functional plant TMs, besides the bilayer, contain large amounts of non-bilayer lipid phases. Bulk lipids have been shown to be associated with lumenal, stromal-side and marginal-region proteins and proposed to play roles in the self-assembly and photoprotection of the photosynthetic machinery. Furthermore, it has recently been pointed out that the generation and utilization of pmf for ATP synthesis according to the 'protet' or protonic charge transfer model Kell (Biochim Biophys Acta Bioenerg 1865(4):149504, 2024), requires high MGDG content Garab (Physiol Plant 177(2):e70230, 2025). In this study, to gain better insight into the structural and functional roles of MGDG, we employed all atom and coarse-grained molecular dynamics simulations to explore how temperature, hydration levels and varying MGDG concentrations affect the structural and dynamic properties of bilayer membranes constituted of plant thylakoid lipids. Our findings reveal that MGDG promotes increased membrane fluidity and dynamic fluctuations in membrane thickness. MGDG-rich stacked bilayers spontaneously formed inverted hexagonal phases; these transitions were enhanced at low hydration levels and at elevated but physiologically relevant temperatures. It can thus be inferred that MGDG plays important roles in heat and drought stress mechanisms.
在产氧光合生物中，光反应由嵌入类囊体膜（TMs）脂质双层中的蛋白质复合物进行。大量脂质分子组织成双层结构为质子动力势（pmf）的形成及其用于ATP合成提供了最佳条件。然而，TMs的脂质组成以非双层脂质单半乳糖基二酰基甘油（MGDG）为主，并且功能性植物TMs除了双层外还含有大量非双层脂质相。已表明大量脂质与腔面、基质侧和边缘区域的蛋白质相关，并提出其在光合机器的自组装和光保护中发挥作用。此外，最近有人指出，根据“protet”或质子电荷转移模型Kell（《生物化学与生物物理学报：生物能量学》1865(4):149504, 2024），pmf用于ATP合成的产生和利用需要高MGDG含量Garab（《植物生理学》177(2):e70230, 2025）。在本研究中，为了更好地了解MGDG的结构和功能作用，我们采用全原子和粗粒度分子动力学模拟来探索温度、水合水平和不同MGDG浓度如何影响由植物类囊体脂质构成的双层膜的结构和动力学性质。我们的研究结果表明，MGDG促进膜流动性增加和膜厚度的动态波动。富含MGDG的堆叠双层自发形成反相六角相；这些转变在低水合水平和升高但生理相关的温度下增强。因此可以推断，MGDG在热和干旱胁迫机制中起重要作用。
