A small ATPase protein of Arabidopsis, TGD3, involved in chloroplast lipid import
A small ATPase protein of Arabidopsis, TGD3, involved in chloroplast lipid import
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DOI：
10.1074/jbc.m704063200
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发表时间：
2007-12-07
影响因子：
4.8
通讯作者：
Benning, Christoph
中科院分区：
文献类型：
--
作者：
Lu, Binbin;Xu, Changcheng;Benning, Christoph
在真核细胞中，极性脂类转运是必不可少的，因为脂类组装膜通常不同于最终目的地膜。一个明显的例子是植物叶绿体中光合膜(类囊体膜)的生物发生。内质网和内、外质体膜上的脂类生物合成酶也参与其中。这种划分需要广泛的脂类贩运。拟南芥的突变体可以用来干扰内质网衍生的类囊体脂前体与类囊体脂的结合。其中两个突变体TGD1和TGD2分别编码叶绿体内膜脂转运蛋白的渗透酶和底物结合组分。在这里，我们描述了拟南芥的第三个蛋白，TGD3，一个小的ATPase，被认为是这个转运子的一部分。与tgd1和tgd2突变体一样，三酰甘油和三乳糖脂在携带TGD3编码区5‘端T-DNA插入的tgd3突变体中积累。TGD3蛋白具有基本的ATPase活性，定位于叶绿体内膜外的叶绿体内。与TGD1、-2和-3同源的蛋白质被预测存在于革兰氏细菌中，并且各自的基因被组织在操纵子中，这表明基因产物具有共同的生化作用。根据目前的分析，推测TGD3是拟南芥合成内质网衍生类囊体脂所必需的脂类转运蛋白中缺失的ATPase组分，涉及TGD1和TGD2。
Polar lipid trafficking is essential in eukaryotic cells as membranes of lipid assembly are often distinct from final destination membranes. A striking example is the biogenesis of the photosynthetic membranes (thylakoids) in plastids of plants. Lipid biosynthetic enzymes at the endoplasmic reticulum and the inner and outer plastid envelope membranes are involved. This compartmentalization requires extensive lipid trafficking. Mutants of Arabidopsis are available that are disrupted in the incorporation of endoplasmic reticulum-derived lipid precursors into thylakoid lipids. Two proteins affected in two of these mutants, trigalactosyldiacylglycerol 1 (TGD1) and TGD2, encode the permease and substrate binding component, respectively, of a proposed lipid translocator at the inner chloroplast envelope membrane. Here we describe a third protein of Arabidopsis, TGD3, a small ATPase proposed to be part of this translocator. As in the tgd1 and tgd2 mutants, triacylglycerols and trigalactolipids accumulate in a tgd3 mutant carrying a T-DNA insertion just 5' of the TGD3 coding region. The TGD3 protein shows basal ATPase activity and is localized inside the chloroplast beyond the inner chloroplast envelope membrane. Proteins orthologous to TGD1, -2, and -3 are predicted to be present in Gram - bacteria, and the respective genes are organized in operons suggesting a common biochemical role for the gene products. Based on the current analysis, it is hypothesized that TGD3 is the missing ATPase component of a lipid transporter involving TGD1 and TGD2 required for the biosynthesis of ER-derived thylakoid lipids in Arabidopsis.