The Arabidopsis thaliana type I isopentenyl diphosphate isomerases are targeted to multiple subcellular compartments and have overlapping functions in isoprenoid biosynthesis
The Arabidopsis thaliana type I isopentenyl diphosphate isomerases are targeted to multiple subcellular compartments and have overlapping functions in isoprenoid biosynthesis
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DOI：
10.1105/tpc.107.053926
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发表时间：
2008-03-01
期刊：
影响因子：
11.6
通讯作者：
Pichersky, Eran
中科院分区：
文献类型：
--
作者：
Phillips, Michael A.;D'Auria, John C.;Pichersky, Eran
为了形成类异戊二烯的组成部分，异戊烯基二磷酸 (IPP) 异构酶活性（将 IPP 转化为二甲基烯丙基二磷酸 (DMAPP)）似乎在细胞质、质体和线粒体中是必需的。拟南芥仅含有两种 IPP 异构酶（异戊烯基二磷酸异构酶 1 [IDI1] 和 IDI2）。两者都编码具有与转运肽相似的 N 末端延伸的蛋白质，并且在所有器官中表达，其中 IDI1 的丰度低于 IDI2。对增强型绿色荧光蛋白融合体的检查表明，IDI1 主要存在于质体中，而 IDI2 主要存在于线粒体中。这两种蛋白质也存在于胞质溶胶中，因为它们是从缺乏转运肽的天然存在的较短转录物翻译而来的，如 cDNA 末端克隆的 5' 快速扩增所证明的那样。当施用标记的甲羟戊酸时，细胞质中的IPP异构酶活性通过细胞质类异戊二烯产物谷甾醇的IPP和DMAPP衍生单位的统一标记来证实。对突变株系的分析表明，双突变体无法存活，而纯合单突变体与野生型没有主要的形态或化学差异，除了 idi2 突变体上的花具有融合的萼片和不发达的花瓣之外。因此，两种拟南芥IPP异构酶中的每一种都存在于多个但部分重叠的亚细胞位置中，并且每一种都可以通过胞质溶胶中的部分冗余来补偿另一种异构酶的损失。
To form the building blocks of isoprenoids, isopentenyl diphosphate (IPP) isomerase activity, which converts IPP to dimethylallyl diphosphate (DMAPP), appears to be necessary in cytosol, plastids, and mitochondria. Arabidopsis thaliana contains only two IPP isomerases (Isopentenyl Diphosphate Isomerase1 [IDI1] and IDI2). Both encode proteins with N-terminal extensions similar to transit peptides and are expressed in all organs, with IDI1 less abundant than IDI2. Examination of enhanced green fluorescent protein fusions established that IDI1 is mainly in the plastid, whereas IDI2 is mainly in the mitochondria. Both proteins are also in the cytosol as a result of their translation from naturally occurring shorter transcripts lacking transit peptides, as demonstrated by 5' rapid amplification of cDNA ends cloning. IPP isomerase activity in the cytosol was confirmed by uniform labeling of IPP- and DMAPP-derived units of the cytoplasmic isoprenoid product, sitosterol, when labeled mevalonate was administered. Analysis of mutant lines showed that double mutants were nonviable, while homozygous single mutants had no major morphological or chemical differences from the wild type except for flowers with fused sepals and underdeveloped petals on idi2 mutants. Thus, each of the two Arabidopsis IPP isomerases is found in multiple but partially overlapping subcellular locations, and each can compensate for the loss of the other through partial redundancy in the cytosol.