Heme A and cytochrome oxidase biosynthesis

血红素 A 和细胞色素氧化酶生物合成

• 批准号: 6685299
• 负责人: ALEXANDER A TZAGOLOFF
• 金额: $ 25.07万
• 依托单位: COLUMBIA UNIV NEW YORK MORNINGSIDE
• 依托单位国家: 美国
• 财政年份: 1994
• 资助国家: 美国
• 起止时间: 1994-01-15 至 2006-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6685299
• 关键词: Heme; cytochrome; oxidase; biosynthesis

DESCRIPTION (provided by applicant): Cytochrome oxidase (COX), the terminal respiratory complex of mitochondria, is composed of 12-13 subunits three of which, encoded by mtDNA, form the catalytic core of the enzyme. In S. cerevisiae, biogenesis of the complex is governed by some 3 dozen nuclear genes. These code for the set of imported subunits and for various accessory factors involved in expression of the catalytic subunits, membrane insertion and maturation of subunit 2 (copper protein), heme A synthesis, copper homeostasis, and still other events that are poorly defined at present. During the past grant period we: 1) obtained evidence that Cox15p, ferredoxin and ferredoxin reductase constitute a three component monooxygenase that converts heme O to the immediate precursor of heme A, 2) identified two new genes (COX18, COX2O) responsible for promoting membrane insertion and maturation of subunit 2, 3) characterized suppressors of shy1 mutants whose phenotype implicate subunit 1 (heme protein) as the target of Shy1p action, 4) collaborated with Dr. Pierre Rustin and his colleagues in demonstrating that the COX deficiency of a family with a history of a fatal neuromyopathy is caused by a mutation in heme:famesyl transferase. Our goals for this coming period is to complete studies on the heme A biosynthetic pathway, to continue the analysis of shy1 mutants and the remaining dozen nuclear genes whose functions in COX assembly remain largely unknown. With respect to heme A biosynthesis, we intend to obtain more direct evidence for the participation of ferredoxin in hydroxylation of heme O, to purify and characterize Cox15p, and to identify the hydroxylated precursor of heme A. Secondly, we will strive to gain better insights into the function of Shy1p by examining the assembly intermediates in shy1 mutants through pulse-chase experiments and by searching for new suppressors. These studies should also shed light on the biochemical basis of Leigh's syndrome, which has been shown to be caused by mutations in SURF1, the human homologue of SHY1. Together with the ongoing functional analysis of other COX-specific genes, these studies are anticipated to fill the existent gaps in our understanding of how this important enzyme is assembled.

描述（由申请人提供）：细胞色素氧化酶（COX）是线粒体的末端呼吸复合体，由12-13个亚基组成，其中3个亚基由mtDNA编码，形成酶的催化核心。在酿酒酵母中，复合体的生物发生是由大约36个核基因控制的。这些编码是一组输入亚基和各种辅助因子的编码，这些辅助因子涉及催化亚基的表达、亚基2（铜蛋白）的膜插入和成熟、血红素A合成、铜稳态以及其他目前尚未明确的事件。在过去的资助期内，我们：1)获得了Cox15p、铁氧还蛋白和铁氧还蛋白还原酶组成一个三组分单加氧酶的证据，将血红素O转化为血红素a的直接前体；2)发现了两个新基因（COX18、COX2O），负责促进亚基2的膜插入和成熟；3)鉴定了shy1突变体的抑制因子，其表型暗示亚基1（血红素蛋白）是Shy1p作用的靶标。4)与Pierre Rustin博士和他的同事合作，证明了一个有致命性神经肌病病史的家庭的COX缺乏是由血红素：家族基转移酶突变引起的。在接下来的一段时间里，我们的目标是完成血红素A生物合成途径的研究，继续分析shy1突变体和其余12个在COX组装中功能未知的核基因。在血红素A的生物合成方面，我们将获得铁氧还蛋白参与血红素O羟基化的更直接证据，纯化和表征Cox15p，鉴定血红素A的羟基化前体。其次，我们将通过脉冲追踪实验检测shy1突变体中的组装中间体，并寻找新的抑制因子，以更好地了解Shy1p的功能。这些研究还揭示了Leigh综合征的生化基础，该综合征已被证明是由SURF1突变引起的，SURF1是SHY1的人类同系物。与其他cox特异性基因的功能分析一起，这些研究有望填补我们对这种重要酶如何组装的理解中的空白。