Learned R M, Fink G R
Whitehead Institute for Biomedical Research, Cambridge, MA 02142.
Proc Natl Acad Sci U S A. 1989 Apr;86(8):2779-83. doi: 10.1073/pnas.86.8.2779.
We have isolated the Arabidopsis thaliana gene (HMG1) encoding 3-hydroxy-3-methylglutaryl-CoA reductase [HMG-CoA reductase; (S)-mevalonate:NAD+ oxido-reductase (CoA-acylating), EC 1.1.1.88], the catalyst of the first committed step in isoprenoid biosynthesis. cDNA copies of the plant gene were identified by hybridization with a short, highly conserved segment of yeast HMG-CoA reductase as probe. DNA sequence analysis reveals that the COOH-terminal domain of the Arabidopsis HMG-CoA reductase (containing the catalytic site of the enzyme) is highly conserved with respect to the yeast, mammalian, and Drosophila enzymes, whereas the membrane-bound amino terminus of the Arabidopsis protein is truncated and lacks the complex membrane-spanning architecture of the yeast and animal reductases. Expression of the Arabidopsis gene from the yeast GAL1 promoter in a yeast mutant lacking HMG-CoA reductase activity suppresses the growth defect of the yeast mutant. Taken together, the sequence similarity to other cloned HMG-CoA reductase genes and the suppression of the yeast hmg- mutant provide strong evidence that the novel Arabidopsis gene we have cloned encodes a functional HMG-CoA reductase enzyme.
我们已经分离出了拟南芥基因（HMG1），该基因编码3-羟基-3-甲基戊二酰辅酶A还原酶[HMG-CoA还原酶；（S）-甲羟戊酸：NAD+氧化还原酶（辅酶A酰化），EC 1.1.1.88]，这是类异戊二烯生物合成中第一个关键步骤的催化剂。通过用酵母HMG-CoA还原酶的一个短的、高度保守的片段作为探针进行杂交，鉴定出了该植物基因的cDNA拷贝。DNA序列分析表明，拟南芥HMG-CoA还原酶的COOH末端结构域（包含该酶的催化位点）与酵母、哺乳动物和果蝇的酶高度保守，而拟南芥蛋白的膜结合氨基末端被截断，缺乏酵母和动物还原酶复杂的跨膜结构。在缺乏HMG-CoA还原酶活性的酵母突变体中，由酵母GAL1启动子表达拟南芥基因可抑制该酵母突变体的生长缺陷。综上所述，与其他克隆的HMG-CoA还原酶基因的序列相似性以及对酵母hmg-突变体的抑制作用提供了有力证据，表明我们克隆的这个新的拟南芥基因编码一种功能性的HMG-CoA还原酶。
