Understanding the Mechanisms of Respiratory Supercomplexes and mitochondrial Complex I

项目总结/摘要 线粒体氧化磷酸化电子传递链（ETC）由五个大的 膜蛋白复合物（C1、CII、CIII 2、CIV和CV），并负责大多数膜蛋白复合物的产生。 细胞的ATP。因此，ETC对生物能量代谢至关重要。ETC缺陷是 最常见的诊断为先天性代谢缺陷，CI缺陷约占三分之一， 这些诊断。尽管约50%的CI缺陷患者在生命的前2年内死亡， 约25%的患者达到10岁，CI仍然是所有ETC复合物中机制理解最少的。 此外，尽管有很大的医疗需求，但目前还没有有效的治疗CI或其他ETC的方法 缺陷这种差异部分源于对蛋白质的分子机制的不完全理解。 单个复合物及其高阶组装成超复合物（SC）。在哺乳动物心脏中 大多数CI与CIII 2和CIV（SC I+ III 2 +IV，线粒体）相关，或与CIII 2和CIV（SC I+ III 2 +IV，线粒体）相关。 与CIII 2（SC I+ III 2）结合。最近的生物化学和结构工作产生了第一个原子- 解析哺乳动物线粒体CI的结构，并定义了单个复合物的排列 和SC I+ III 2。然而，关于功能、机制仍然存在重大问题 以及ETC复合物和SC的调节。为了解决我们理解中的这些差距并发展 基础科学，将支持ETC缺陷的潜在治疗策略，我们将建立两个主要的 我实验室的研究方向。使用详细的生化和酶分析以及单颗粒 冷冻电镜结构表征，我们将阐明的机制，功能和 1）分离的CI和2）呼吸SC的调节。为了实现这一目标，我们建议进行系统的 从哺乳动物线粒体中纯化的呼吸道CI和SC的功能和结构比较（来自 HeLa细胞培养物和猪心脏组织）、α-变形菌属副球菌和真菌 模型系统粗糙脉孢菌。P. pacleficans是最接近祖先的生物之一- 在内共生事件之后起源于线粒体的变形菌。N.克拉萨是一家老牌的， 强大的遗传和生物化学系统的生物能量学，但没有高分辨率ETC 结构可用。比较来自这些不同且遗传上易处理的生物体的CI和SC 将使我们能够测试该领域的几个关键机制假设， 确定CI和SC机制和调节的保守特征。这将提供深入了解 CI的能量转换机制和SC形成的生理作用，这将定义科学的 为开发针对CI和进一步ETC缺陷的治疗策略奠定了基础。

PROJECT SUMMARY/ABSTRACT The mitochondrial oxidative phosphorylation electron transport chain (ETC) is composed of five large membrane protein complexes (CI, CII, CIII2, CIV and CV) and is responsible for the production of the majority of cellular ATP. Consequently, the ETC is essential to bioenergetic metabolism. ETC defects are one of the most commonly diagnosed congenital metabolic defects, with CI deficiencies representing roughly a third of these diagnoses. Although ~50% of patients with CI deficiencies die within the first 2 years of life and only ~25% reach 10 years of age, CI remains the least well mechanistically understood of all the ETC complexes. Furthermore, despite the large medical need, there are currently no effective treatments for CI or other ETC deficiencies. This discrepancy stems in part from an incomplete understanding of the molecular mechanisms of the individual complexes and their higher-order assemblies into supercomplexes (SCs). In mammalian heart mitochondria the majority of CI is found in association with CIII2 and CIV (SC I+III2+IV, the respirasome) or in association with CIII2 (SC I+III2). Recent biochemical and structural work has produced the first atomic- resolution structures of mammalian mitochondrial CI and defined the arrangement of the individual complexes within the respirasome and SC I+III2. However, significant questions remain regarding the function, mechanism and regulation of the ETC complexes and SCs. To address these gaps in our understanding and to develop the basic science that will underpin potential treatment strategies of ETC defects, we will establish two major research directions in my lab. Using detailed biochemical and enzymatic analyses together with single particle cryo-electron microscopy structural characterizations, we will elucidate the mechanisms, functions and regulation of 1) isolated CI and 2) respiratory SCs. To achieve this, we propose to perform systematic functional and structural comparisons of respiratory CI and SCs purified from mammalian mitochondria (from both HeLa cell culture and porcine heart tissue), the a-proteobacteria Paracoccus denitrificans and the fungal model system Neurospora crassa. P. denitrificans is one of the closest living organisms to the ancestral a- proteobacteria that originated mitochondria after the endosymbiotic event. N. crassa is an established, powerful genetic and biochemical system for bioenergetics, for which nonetheless no high-resolution ETC structures are available. Comparing the CI and SCs from these divergent and genetically tractable organisms to their mammalian counterparts will allow us to test several key mechanistic hypotheses in the field and to identify the conserved features of CI and SC mechanism and regulation. This will provide deep insights into the energy-converting mechanism of CI and the physiological roles of SC formation, which will define the scientific foundation needed for the development of therapeutic strategies against CI and further ETC deficiencies.