FUNCTIONAL ROLES OF COENZYME Q IN YEAST AND HUMAN CELLS

辅酶Q或Q在细胞中作为线粒体和血浆的氧化还原活性辅酶发挥作用 膜电子传递，以及一种必需的脂溶性抗氧化剂。人类饮食 补充Q似乎对减缓神经和肌肉的进展有有益的效果 退行性疾病。细胞能够合成Q，但关于这些位点仍有许多需要了解的地方 它的合成、细胞内和细胞内转运机制以及它的调节和酶学 生物合成。拟议研究的目标是表征q生物合成的多肽。 途径，并确定Q生物合成的酶学。该实验系统利用了九个 酿酒酵母中Q-缺失(CoQ)突变体的互补群。COQ 突变体为在酵母和哺乳动物中鉴定辅酶Q多肽提供了基础。 Q-中间体的合成类似物提供的试剂既可用作分离的标准，也可用作 Q中间体的鉴定，并作为酶活性测定的底物。遗传和生化 有证据表明，在酵母中合成Q需要线粒体辅酶Q多酶复合体。我们 建议鉴定多肽成分，并确定Q-中间体是否构成 这些复合体的重要脂类成分。辅酶Q生物合成的一个潜在的重要功能 复合体是通过该途径调节Q和Q中间体的流量，这一过程可能 影响呼吸电子传输链的性能。我们还将描述一个十分之一 酵母突变体的互补组。酵母coqIO突变体定义了一种独特的呼吸缺陷 因为线粒体表现出Q定义的特征表型，但却有正常的Q水平。 一类突变体在Q结合蛋白中存在缺陷，该蛋白与起始结构域蛋白具有同源性。我们 将确定这个Q结合蛋白是否在Q从它的 合成到呼吸电子传递的适当位置。该实验方法使用一个 结合脂肪化学、酵母遗传学和生物化学来描述生物合成步骤 负责在酵母和人类细胞中生产Q。

Ubiquinone (coenzyme Q or Q) functions in cells as a redox-active coenzyme of mitochondrial and plasma membrane electron transport, as well as an essential lipid soluble antioxidant. Human dietary supplementation with Q appears to have beneficial effects in slowing the progression of neuro- and muscle- degenerative diseases. Cells are capable of synthesizing Q, but much remains to be learned about the sites of its synthesis, mechanisms of inter- and intra-cellular transport, and the regulation and enzymology of its biosynthesis. The goals of the proposed research are to characterize the polypeptides of the Q biosynthetic pathway and to define the enzymology of Q biosynthesis. The experimental system takes advantage of nine complementation groups of Q-deficient (coq) mutants in the yeast Saccharomyces cerevisiae. The coq mutants provide the basis for the characterization of the Coq polypeptides in both yeast and mammals. Synthetic analogs of Q-intermediates provide reagents that serve both as standards in the isolation and identification of Q intermediates, and as substrates for assays of enzyme activities. Genetic and biochemical evidence indicate that synthesis of Q in yeast requires a mitochondrial Coq multienzyme complex. We propose to identify the polypeptide components, and to determine whether Q-intermediates constitute important lipid components of these complexes. A potentially important function of the Coq biosynthetic complex is to regulate the flux of Q and Q-intermediates through the pathway, a process that potentially impacts performance of the respiratory electron transport chain. We will also characterize a tenth complementation group of yeast mutants. The yeast coqIO mutant defines a unique respiratory deficiency because mitochondria exhibit the characteristic phenotype of Q-defiency, yet have normal levels of Q. This class of mutants has a defect in a Q binding protein that shares homology with START domain proteins. We will determine whether this Q binding protein functions as a chaperone in the delivery of Q from its site of synthesis to its proper location for respiratory electron transport. The experimental approach employs a combination of lipid chemistry, yeast genetics, and biochemistry to delineate the biosynthetic steps responsible for the production of Q in yeast and human cells.