拟南芥叶绿体被膜中半乳糖脂的合成与转运
Synthesis and transfer of galactolipids in the chloroplast envelope membranes of Arabidopsis thaliana.
作者信息
Kelly Amélie A, Kalisch Barbara, Hölzl Georg, Schulze Sandra, Thiele Juliane, Melzer Michael, Roston Rebecca L, Benning Christoph, Dörmann Peter
机构信息
Department of Molecular Physiology, Max Planck Institute of Molecular Plant Physiology, 14476 Potsdam, Germany;
Department of Molecular Biotechnology, Institute of Molecular Physiology and Biotechnology of Plants, University of Bonn, 53115 Bonn, Germany;
出版信息
Proc Natl Acad Sci U S A. 2016 Sep 20;113(38):10714-9. doi: 10.1073/pnas.1609184113. Epub 2016 Sep 6.
Galactolipids [monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG)] are the hallmark lipids of photosynthetic membranes. The galactolipid synthases MGD1 and DGD1 catalyze consecutive galactosyltransfer reactions but localize to the inner and outer chloroplast envelopes, respectively, necessitating intermembrane lipid transfer. Here we show that the N-terminal sequence of DGD1 (NDGD1) is required for galactolipid transfer between the envelopes. Different diglycosyllipid synthases (DGD1, DGD2, and Chloroflexus glucosyltransferase) were introduced into the dgd1-1 mutant of Arabidopsis in fusion with N-terminal extensions (NDGD1 and NDGD2) targeting to the outer envelope. Reconstruction of DGDG synthesis in the outer envelope membrane was observed only with diglycosyllipid synthase fusion proteins carrying NDGD1, indicating that NDGD1 enables galactolipid translocation between envelopes. NDGD1 binds to phosphatidic acid (PA) in membranes and mediates PA-dependent membrane fusion in vitro. These findings provide a mechanism for the sorting and selective channeling of lipid precursors between the galactolipid pools of the two envelope membranes.
半乳糖脂类[单半乳糖基二酰基甘油（MGDG）和双半乳糖基二酰基甘油（DGDG）]是光合膜的标志性脂质。半乳糖脂合酶MGD1和DGD1催化连续的半乳糖基转移反应，但分别定位于叶绿体的内膜和外膜，这就需要膜间脂质转移。在这里，我们表明DGD1的N端序列（NDGD1）是包膜间半乳糖脂转移所必需的。将不同的二糖基脂合酶（DGD1、DGD2和绿屈挠菌葡糖基转移酶）与靶向外膜的N端延伸序列（NDGD1和NDGD2）融合，导入拟南芥的dgd1-1突变体中。仅在携带NDGD1的二糖基脂合酶融合蛋白中观察到外膜中DGDG合成的重建，这表明NDGD1能够实现包膜间半乳糖脂的转运。NDGD1在膜中与磷脂酸（PA）结合，并在体外介导PA依赖的膜融合。这些发现为脂质前体在两个包膜膜的半乳糖脂库之间的分选和选择性转运提供了一种机制。
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