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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >The Arabidopsis LUT1 locus encodes a member of the cytochrome P450 family that is required for carotenoid ε-ring hydroxylation activity
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The Arabidopsis LUT1 locus encodes a member of the cytochrome P450 family that is required for carotenoid ε-ring hydroxylation activity

机译：拟南芥LUT1基因座编码类胡萝卜素ε环羟基化活性所需的细胞色素P450家族成员

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摘要

Lutein, a dihydroxy xanthophyll, is the most abundant carotenoid in plant photosynthetic tissues and plays crucial structural and functional roles in the light-harvesting complexes. Carotenoid β-and ε-hydroxylases catalyze the formation of lutein from α-caro-tene (β,e-carotene). In contrast to the well studied β-hydroxylases that have been cloned and characterized from many organisms, the ε-hydroxylase has only been genetically defined by the Iut1 mutation in Arabidopsis. We have isolated the LUT1 gene by positional cloning and found that, in contrast to all known carotenoid hydroxylases, which are the nonheme diiron monooxygenases, LUT1 encodes a cytochrome P450-type monooxygenase, CYP97C1. Introduction of a null mutant allele of LUT1, lut1-3, into the β-hydroxylase 1/β-hydroxylase 2 (b1 62) double-mutant background, in which both Arabidopsis β-hydroxylases are disrupted, yielded a genotype (lut1-3 b1 b2) in which all three known carotenoid hydroxylase activities are eliminated. Surprisingly, hydroxy-lated β-rings were still produced in lut1-3 b1 b2, suggesting that a fourth unknown carotenoid β-hydroxylase exists in vivo that is structurally unrelated to β-hydroxylase 1 or 2. A second chloro-plast-targeted member of the CYP97 family, CYP97A3, is 49% identical to LUT1 and hypothesized as a likely candidate for this additional β-ring hydroxylation activity. Overall, LUT1 defines a class of carotenoid hydroxylases that has evolved independently from and uses a different mechanism than nonheme diiron β-hydroxylases.
机译：叶黄素是一种二羟基叶黄素，是植物光合组织中含量最丰富的类胡萝卜素，在光捕获复合物中起着至关重要的结构和功能作用。类胡萝卜素的β-和ε-羟基酶催化由α-胡萝卜素（β，e-胡萝卜素）形成叶黄素。与已经从许多生物体中克隆并表征的经过深入研究的β-羟化酶相反，ε-羟化酶仅在遗传上由拟南芥中的Iut1突变定义。我们已经通过位置克隆分离了LUT1基因，发现与所有已知的类胡萝卜素羟化酶（非血红素二铁单加氧酶）相反，LUT1编码一种细胞色素P450型单加氧酶CYP97C1。将LUT1的无效突变体等位基因lut1-3引入β-羟化酶1 /β-羟化酶2（b1 62）双突变背景中，其中两个拟南芥β-羟化酶均被破坏，产生基因型（lut1-3 b1 b2），其中所有三个已知的类胡萝卜素羟化酶活性均被消除。出乎意料的是，在lut1-3 b1 b2中仍产生羟基化的β-环，这表明体内存在与β-羟化酶1或2结构上不相关的第四种未知的类胡萝卜素β-羟化酶。第二种以叶绿体为目标的成员CYP97家族的CYP97A3与LUT1具有49％的相同性，并被认为是这种额外的β环羟基化活性的可能候选者。总体而言，LUT1定义了一类类胡萝卜素羟化酶，该类类胡萝卜素与非血红素二铁β-羟化酶独立进化并采用不同的机制。

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