Isolation and functional expression of human COQ3, a gene encoding a methyltransferase required for ubiquinone biosynthesis
Isolation and functional expression of human COQ3, a gene encoding a methyltransferase required for ubiquinone biosynthesis
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DOI：
10.1074/jbc.275.17.12381
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发表时间：
2000-04-28
影响因子：
4.8
通讯作者：
Clarke, CF
中科院分区：
文献类型：
--
作者：
Jonassen, T;Clarke, CF
酿酒酵母中的COQ3基因编码一种O-甲基转移酶，在辅酶Q的生物合成途径中需要两个步骤。这种酶将早期的Q中间体3，4-二羟基-6-聚戊烯基苯甲酸甲基化，以及途径中的最终中间体，将去甲基-Q转化为Q，该酶还能够甲基化独特的原核生物早期中间体2-羟基-6-聚戊烯基苯酚。通过与大鼠COQ3的序列同源性，从人心脏cDNA文库中克隆了编码人COQ3同源物的全长cDNA。该克隆含有一个933个碱基对的开放阅读框，编码的多肽与真核和原核生物的Coq3同源物有很大的序列一致性，在人类序列89到255氨基酸之间的区域，大鼠和人的同源物有87%的同源性，而人和酵母的同源物有35%的同源性。当以多拷贝形式表达时，人的构建体挽救了酵母coq3缺失突变体在非发酵碳源上的生长，并恢复了辅酶Q的生物合成，尽管水平低于野生型酵母。以辅酶Q生物合成途径中间产物的法尼化类似物为底物的体外甲基转移酶检测表明，在所有三种底物的测试下，人的酶都是活性的。
The COQ3 gene in Saccharomyces cerevisiae encodes an O-methyltransferase required for two steps in the biosynthetic pathway of ubiquinone (coenzyme Q, or Q). This enzyme methylates an early Q intermediate, 3,4-dihydroxy-6-polyprenylbenzoic acid, as well as the final intermediate in the pathway, converting demethyl-Q to Q, This enzyme is also capable of methylating the distinct prokaryotic early intermediate 2-hydroxy-6-polyprenyl phenol. A full-length cDNA encoding the human homologue of COQ3 was isolated from a human heart cDNA library by sequence homology to rat Coq3. The clone contained a 933-base pair open reading frame that encoded a polypeptide with a great deal of sequence identity to a variety of eukaryotic and prokaryotic Coq3 homologues, In the region between amino acids 89 and 255 in the human sequence, the rat and human homologues are 87% identical, whereas human and yeast are 35% identical. When expressed in multicopy, the human construct rescued the growth of a yeast coq3 null mutant on a nonfermentable carbon source and restored coenzyme Q biosynthesis, although at lower levels than that of wild type yeast. In vitro methyltransferase assays using farnesylated analogues of intermediates in the coenzyme Q biosynthetic pathway as substrates showed that the human enzyme is active with all three substrates tested.