Structure and membrane interactions of Arabidopsis thaliana DGD2, a glycosyltransferase in the chloroplast membrane.

IF 4 2区 生物学 Q2 BIOCHEMISTRY & MOLECULAR BIOLOGY
Emma Scaletti Hutchinson, Markel Martínez-Carranza, Biao Fu, Lena Mäler, Pål Stenmark
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Abstract

Galactolipids are characteristic lipids of the photosynthesis membranes of higher plants and cyanobacteria. Due to their close relationship to the stability of the photosystem protein complexes, the biogenesis of galactolipids has been intensively studied on the genetic and molecular levels. There are two major types of galactolipids in chloroplastic membranes: monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG). Under phosphate-limiting conditions, the amount of DGDG increases dramatically to allow for phosphate salvage from phospholipids. In Arabidopsis thaliana, the membrane-associated glycosyltransferase Digalactosyldiacylglycerol synthase 2 (atDGD2) is highly responsive to phosphate starvation and is significantly upregulated during such conditions. The lipid galactosylation reactions are also fundamentally interesting as they require a catalyst that is capable of bringing a hydrophilic and lipophilic substrate together at the solution-membrane phase border. Here we present the X-ray crystal structure of atDGD2, which is the first reported DGDG synthase structure. AtDGD2 is most structurally similar to functionally unrelated GT-B enzymes. Interestingly, in spite of significant donor substrate binding differences we identified four amino acids (Gly22, His151, Lys243 and Glu321, atDGD2 numbering) which were entirely conserved between the structurally similar enzymes. We also investigated the membrane interaction kinetics and membrane anchoring mechanism of atDGD2. This demonstrated that atDGD2 is membrane-bound, but also showed that membrane binding is highly dynamic. Furthermore, our structural information in context of previous biophysical studies highlights regions of the enzyme exhibiting a high degree of structural plasticity, which we propose to be important for allowing atDGD2 to quickly adapt its activity based on the membrane lipid environment.

拟南芥叶绿体膜糖基转移酶DGD2的结构和膜相互作用。
半乳脂是高等植物和蓝藻光合作用膜的特征脂类。由于它们与光系统蛋白复合物的稳定性密切相关,半乳糖脂的生物发生已经在遗传和分子水平上得到了深入的研究。在叶绿体膜中有两种主要的半乳糖脂:单半乳糖二酰基甘油(MGDG)和双半乳糖二酰基甘油(DGDG)。在限制磷酸盐的条件下,DGDG的数量急剧增加,以允许磷脂中的磷酸盐回收。在拟南芥中,膜相关糖基转移酶二半乳糖二酰基甘油合成酶2 (atDGD2)对磷酸盐饥饿高度敏感,并在这种情况下显著上调。脂质半乳糖基化反应从根本上来说也很有趣,因为它们需要一种催化剂,能够在溶液-膜相边界将亲水和亲脂的底物结合在一起。这里我们展示了atDGD2的x射线晶体结构,这是首次报道的DGDG合成酶结构。AtDGD2在结构上与功能无关的GT-B酶最为相似。有趣的是,尽管供体底物结合存在显著差异,但我们发现了四个氨基酸(Gly22, His151, Lys243和Glu321, atDGD2编号)在结构相似的酶之间完全保守。我们还研究了atDGD2的膜相互作用动力学和膜锚定机制。这表明atDGD2是膜结合的,但也表明膜结合是高度动态的。此外,在之前的生物物理研究背景下,我们的结构信息强调了酶的高度结构可塑性区域,我们认为这对于允许atDGD2根据膜脂环境快速适应其活性是重要的。
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来源期刊
Journal of Biological Chemistry
Journal of Biological Chemistry Biochemistry, Genetics and Molecular Biology-Biochemistry
自引率
4.20%
发文量
1233
期刊介绍: The Journal of Biological Chemistry welcomes high-quality science that seeks to elucidate the molecular and cellular basis of biological processes. Papers published in JBC can therefore fall under the umbrellas of not only biological chemistry, chemical biology, or biochemistry, but also allied disciplines such as biophysics, systems biology, RNA biology, immunology, microbiology, neurobiology, epigenetics, computational biology, ’omics, and many more. The outcome of our focus on papers that contribute novel and important mechanistic insights, rather than on a particular topic area, is that JBC is truly a melting pot for scientists across disciplines. In addition, JBC welcomes papers that describe methods that will help scientists push their biochemical inquiries forward and resources that will be of use to the research community.
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