Goss Reimund, Latowski Dariusz, Grzyb Joanna, Vieler Astrid, Lohr Martin, Wilhelm Christian, Strzalka Kazimierz
Institute of Biology I, Plant Physiology, University of Leipzig, Johannisallee 21-23, 04103 Leipzig, Germany.
Biochim Biophys Acta. 2007 Jan;1768(1):67-75. doi: 10.1016/j.bbamem.2006.06.006. Epub 2006 Jun 7.
In the present study, the solubility and enzymatic de-epoxidation of diadinoxanthin (Ddx) was investigated in three different artificial membrane systems: (1) Unilamellar liposomes composed of different concentrations of the bilayer forming lipid phosphatidylcholine (PC) and the inverted hexagonal phase (H(II) phase) forming lipid monogalactosyldiacylglycerol (MGDG), (2) liposomes composed of PC and the H(II) phase forming lipid phosphatidylethanolamine (PE), and (3) an artificial membrane system composed of digalactosyldiacylglycerol (DGDG) and MGDG, which resembles the lipid composition of the natural thylakoid membrane. Our results show that Ddx de-epoxidation strongly depends on the concentration of the inverted hexagonal phase forming lipids MGDG or PE in the liposomes composed of PC or DGDG, thus indicating that the presence of inverted hexagonal structures is essential for Ddx de-epoxidation. The difference observed for the solubilization of Ddx in H(II) phase forming lipids compared with bilayer forming lipids indicates that Ddx is not equally distributed in the liposomes composed of different concentrations of bilayer versus non-bilayer lipids. In artificial membranes with a high percentage of bilayer lipids, a large part of Ddx is located in the membrane bilayer. In membranes composed of equal proportions of bilayer and H(II) phase forming lipids, the majority of the Ddx molecules is located in the inverted hexagonal structures. The significance of the pigment distribution and the three-dimensional structure of the H(II) phase for the de-epoxidation reaction is discussed, and a possible scenario for the lipid dependence of Ddx (and violaxanthin) de-epoxidation in the native thylakoid membrane is proposed.
在本研究中，我们研究了二异岩藻黄素（Ddx）在三种不同人工膜系统中的溶解度和酶促脱环氧化作用：（1）由不同浓度的形成双层结构的脂质磷脂酰胆碱（PC）和形成反相六角相（H(II)相）的脂质单半乳糖基二酰基甘油（MGDG）组成的单层脂质体；（2）由PC和形成H(II)相的脂质磷脂酰乙醇胺（PE）组成的脂质体；（3）由二半乳糖基二酰基甘油（DGDG）和MGDG组成的人工膜系统，该系统类似于天然类囊体膜的脂质组成。我们的结果表明，Ddx的脱环氧化作用强烈依赖于由PC或DGDG组成的脂质体中形成反相六角相的脂质MGDG或PE的浓度，因此表明反相六角结构的存在对于Ddx的脱环氧化作用至关重要。与形成双层结构的脂质相比，观察到的Ddx在形成H(II)相的脂质中的溶解差异表明，Ddx在由不同浓度的双层脂质与非双层脂质组成的脂质体中分布不均。在双层脂质比例较高的人工膜中，大部分Ddx位于膜双层中。在由等量的双层脂质和形成H(II)相的脂质组成的膜中，大多数Ddx分子位于反相六角结构中。我们讨论了色素分布和H(II)相的三维结构对脱环氧化反应的重要性，并提出了天然类囊体膜中Ddx（和紫黄质）脱环氧化作用脂质依赖性的一种可能情况。
