FATTY ACID DESATURASE4 of Arabidopsis encodes a protein distinct from characterized fatty acid desaturases
FATTY ACID DESATURASE4 of Arabidopsis encodes a protein distinct from characterized fatty acid desaturases
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DOI：
10.1111/j.1365-313x.2009.04001.x
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发表时间：
2009-12-01
期刊：
影响因子：
7.2
通讯作者：
Benning, Christoph
中科院分区：
文献类型：
--
作者：
Gao, Jinpeng;Ajjawi, Imad;Benning, Christoph
极性膜甘油脂以分子种类的混合物形式存在，所述分子种类由极性头部基团和酯化到甘油主链上的特征性酰基限定。植物叶绿体特有的磷脂酰甘油分子种类在其核心甘油基部分的sn-2位携带δ 3-反式十六碳烯酸。缺失该特定磷脂酰甘油分子种类的拟南芥fad 4 -1突变体缺乏必需的脂肪酸去饱和酶或其组分。在植物中，与膜脂相关的酰基绝大多数含有顺式构型的双键。然而，FAD 4是不寻常的，因为它参与了在棕榈酸的羧基附近引入的反式双键的形成，该反式双键特异性地酯化至磷脂酰甘油的sn-2甘油基碳。作为对这种不寻常的去饱和酶反应的分析的第一步，FAD 4基因被确定为FAD 4基因座的定位和与已知的脂质基因的共表达分析。FAD 4编码一种预测的膜整合蛋白，基于整体序列保守性，该膜整合蛋白似乎与经典的膜结合脂肪酸去饱和酶无关。然而，FAD 4蛋白含有两个类似于金属蛋白如脂肪酸去饱和酶的组氨酸基序。FAD 4靶向质体。在转基因拟南芥中的cDNA的过表达导致相对于野生型磷脂酰甘油中的Δ 3-反式十六烷酰基基团的积累增加。总之，这些结果与FAD 4是一类新的脂肪酸去饱和酶的创始成员的假设是一致的。
P>Polar membrane glycerolipids occur in a mixture of molecular species defined by a polar head group and characteristic acyl groups esterified to a glycerol backbone. A molecular species of phosphatidylglycerol specific to chloroplasts of plants carries a Delta 3-trans hexadecenoic acid in the sn-2 position of its core glyceryl moiety. The fad4-1 mutant of Arabidopsis thaliana missing this particular phosphatidylglycerol molecular species lacks the necessary fatty acid desaturase, or a component thereof. The overwhelming majority of acyl groups associated with membrane lipids in plants contains double bonds with a cis configuration. However, FAD4 is unusual because it is involved in the formation of a trans double bond introduced close to the carboxyl group of palmitic acid, which is specifically esterified to the sn-2 glyceryl carbon of phosphatidylglycerol. As a first step towards the analysis of this unusual desaturase reaction, the FAD4 gene was identified by mapping of the FAD4 locus and coexpression analysis with known lipid genes. FAD4 encodes a predicted integral membrane protein that appears to be unrelated to classic membrane bound fatty acid desaturases based on overall sequence conservation. However, the FAD4 protein contains two histidine motifs resembling those of metalloproteins such as fatty acid desaturases. FAD4 is targeted to the plastid. Overexpression of the cDNA in transgenic Arabidopsis led to increased accumulation of the Delta 3-trans hexadecanoyl group in phosphatidylglycerol relative to wild type. Taken together these results are consistent with the hypothesis that FAD4 is the founding member of a novel class of fatty acid desaturases.