FUNCTIONAL ROLES OF UBIQUINONE IN YEAST AND HUMAN CELLS

泛醌是线粒体呼吸的重要组成部分。 链条。虽然存在于动物的所有器官和组织中，但 泛醌在心肌和骨骼肌中的浓度最高。 泛醌的合成和定位通常被认为是有限的。 到线粒体膜内层。然而，最近的一份报告显示， 这种泛醌也是在大鼠肝脏的内质网上合成的。事实上，高尔基 囊泡和溶酶体，与内质网紧密联系的膜， 在蛋白质的基础上比线粒体含有更多的泛醌。该功能 泛醌可能在这些细胞内的其他隔室中起作用 不清楚。 由于酵母和其他真核生物中的泛醌生物合成共享 同样的途径，拟议的研究利用了一类呼吸道 缺陷型酿酒酵母的缺陷突变株 泛苯二酚。突变体分为9个互补组，并将 用来表征辅酶Q生物合成的调节和 确定非线粒体隔室中泛醌的功能。 3，4-二羟基-5-己烯基苯甲酸酯(DHHB)缺陷酵母突变株 甲基转移酶，泛醌合成的一种受调控的酶，将允许 编码这种酶的基因将被克隆。该基因将提供 研究DHHB调控所需的生化工具 甲基转移酶活性及其在泛醌调控中的作用 生物合成。将构建DHHB甲基转移酶零突变以 评估线粒体泛醌合成不足是否会影响 泛醌在其他细胞器中营养不良或合成。其中的病变 其他泛醌营养缺乏症突变体也将被发现。酵母突变体 菌株将被用作分离人cdna克隆的载体，通过 同源探查策略或功能互补。 已有实验疗法报道，在这些疗法中，给药 心脏病患者的泛醌，线粒体 脑肌病或Kearns-Sayre提示泛醌可能有助于 在预防梅维诺林引起的肌肉无力方面，这是一个罕见但主要的方面 洛伐他汀治疗低胆固醇血症的疗效观察这些机制由 目前尚不清楚是哪种泛醌调节了这些效应。建议进行的研究 应该会增加我们对泛醌在这些物质中的作用的理解 临床疗法。

Ubiquinone is an essential component of the mitochondrial respiratory chain. Although present in all organs and tissues of animals, the concentration of ubiquinone is highest in heart and skeletal muscle. Ubiquinone synthesis and localization is usually considered to be limited to the inner mitochondrial membrane. However, a recent report has shown that ubiquinone is also synthesized on the ER of rat liver. In fact, Golgi vesicles and lysosomes, membranes in close communication with the ER, contain more ubiquinone on a protein basis that mitochondria. The function ubiquinone might be serving in these other intracellular compartments is not clear. Since ubiquinone biosynthesis in yeast and other eukaryotes have share the same pathway, the proposed studies take advantage of a class of respiratory defective mutants of Saccharomyces cerevisiae that are deficient in ubiquinone. The mutants fall into nine complementation groups, and will be used to characterize the regulation of ubiquinone biosynthesis and to determine the function of ubiquinone in nonmitochondrial compartments. Yeast mutants defective in 3,4-dihydroxy-5-hexaprenyl benzoate (DHHB) methyltransferase, a regulated enzyme of ubiquinone synthesis, will allow the gene encoding this enzyme to be cloned. The gene will provide the biochemical tools necessary to study the regulation of DHHB methyltransferase activity and its role in the regulation of ubiquinone biosynthesis. DHHB methyltransferase null mutants will be constructed to assess whether a lack of mitochondrial ubiquinone synthesis affects ubiquinone auxotrophic or synthesis in other organelles. The lesions in other ubiquinone auxotrophic mutants will be identified. The yeast mutant strains will be used as vehicles for isolating human cDNA clones, either by homology probing strategies or by functional complementation. Experimental therapies have been reported in which administration of ubiquinone to patients with heart disease, mitochondrial encephalomyopathies, or with Kearns-Sayre indicates that ubiquinone may aid in preventing mevinolin induced muscle weakness, a rare but major side effect of hypocholesterolemic therapy with lovastatin. The mechanisms by which ubiquinone mediates these effects is not clear. The proposed studies should increase our understanding of how ubiquinone functions in these clinical therapies.