Synthesis and transfer of galactolipids in the chloroplast envelope membranes of Arabidopsis thaliana
Synthesis and transfer of galactolipids in the chloroplast envelope membranes of Arabidopsis thaliana
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DOI：
10.1073/pnas.1609184113
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发表时间：
2016-09-20
影响因子：
11.1
通讯作者：
Doermann, Peter
中科院分区：
文献类型：
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作者：
Kelly, Amelie A.;Kalisch, Barbara;Doermann, Peter
半乳糖脂[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MGD 1和DGD 1催化连续的半乳糖基转移反应，但分别定位于叶绿体内被膜和外被膜，从而需要膜间脂质转移。在这里，我们表明，N-末端序列的DGD 1（NDGD 1）是所需的包膜之间的半乳糖脂转移。将不同的二糖基化磷脂酶（DGD 1、DGD 2和Chloroflexus glucosyltransferase）与靶向外膜的N-末端延伸（NDGD 1和NDGD 2）融合引入拟南芥dgd 1 -1突变体中。仅用携带NDGD 1的二糖脂合酶融合蛋白观察到外包膜中DGDG合成的重建，表明NDGD 1使包膜之间的半乳糖脂易位。NDGD 1在体外与膜中的磷脂酸（PA）结合并介导PA依赖性膜融合。这些发现提供了一种机制，两个包膜膜的半乳糖脂池之间的脂质前体的分选和选择性通道。
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.