Managing Ionic Iron: Molecular Architecture and Mechanism of Cell Iron Metabolism

描述（由申请人提供）：铁的溶液和氧化还原性质使其成为活化其他动力学惰性底物（包括分子氧）的金属辅基，也使离子铁对需氧生物体具有细胞毒性。从酵母到人类的真核生物必须管理亚铁与分子氧的固有反应性和三价铁在水中的不稳定性;铁在从缺血后组织损伤到神经退行性疾病的人类病理学中的经常引用的作用证明了管理离子铁的重要性。我们提出，铁traffieking途径，成功地抑制铁的非生物副反应有两个基本的和相互关联的功能：连续的铁运输组件是空间上连续的，从而在结构上组织，以支持离子铁物种的通道沿着铁代谢途径。该模型将在酿酒酵母（Saccaromyces cerevisiae）中的铁离子途径中的三个步骤进行测试，酿酒酵母是最易处理的真核细胞，可用于该铁代谢模型的系统测试。这三个步骤是：在质膜中，铁还原与铁渗透偶联;在细胞质中，Fe从PM运输到蛋白质受体位点;以及在液泡中，Fe-氧化还原循环与Fe-储存反应偶联，这些反应精确地反映了铁蛋白中发生的反应。一个主要的策略，以确定构象邻接的铁处理蛋白将荧光共振能量转移，我们建议使用FRET检查还原酶和通透酶的合作伙伴在血浆和液泡膜之间的空间关系。量化新到达的Fe的相对分配的主要策略将是使用经工程改造以开启或关闭这些推定的Fe处理蛋白的生产的细胞。酵母HSP 90蛋白、HSP 82和Hsc 82在Fe处理中的新作用被提出;此外，我们认为一氧化氮和谷胱甘肽联合收割机在二亚硝基二硫代-Fe复合物中起重要作用。铁辅基如血红素和Fe/S簇的代谢已取得显著进展;离子铁是这些“笼”铁物种的前体，并负责表征铁和分子氧之间关系的“腐蚀性化学”。了解细胞如何抑制这种化学反应，将对我们最终阐明人类多种病理学的分子基础做出重大贡献，这些病理学通常部分归因于管理不当的离子铁。

DESCRIPTION (provided by applicant): The solution and redox properties of iron that make it the metal prosthetic group of choice for the activation of otherwise kinetically inert substrates, including dioxygen, also make ionic Fe cytotoxic to aerobic organisms. Eukaryotes from yeast to humans have to manage ferrous iron's inherent reactivity with dioxygen and ferric iron's instability in water; the oft-cited role of iron in human pathology from post-ischemic tissue damage to neurodegenerative disease is testament to the importance of managing ionic iron. We propose that the Fe-traffieking pathway that succeeds in suppressing Fe's abiologic side-reactions has two essential and inter-related features: sequential Fe-trafficking components are spatially contiguous and thereby are architecturally organized to support the channeling of ionic Fe species along the Fe-metabolic pathway. This model will be tested at three steps in the ionic Fe pathway in Saccaromyces cerevisiae, the most tractable eukaryotic cell for a systematic test of this Fe-metabolic model. These three steps are: at the plasma membrane where ferrireduction is coupled to iron permeation; in the cytoplasm where Fe is trafficked from the PM to protein acceptor sites; and in the vacuole where Fe-redox cycling is coupled to Fe-storage in reactions that precisely mirror those that occur in ferritin. A primary strategy to ascertain conformational contiguity of Fe-handling proteins will be fluorescence resonance energy transfer; we propose to use FRET to examine the spatial relationships between reductase and permease partners in the plasma and vacuolar membranes. A primary strategy in quantifying the relative partitioning of newly-arrived Fe will be the use of cells engineered to turn on or turn off production of these putative Fe-handling proteins. A new role in Fe- handling is proposed for the yeast HSP90 proteins, Hsp82 and Hsc82; in addition, we suggest that nitric oxide and glutathione combine in a dinitrosyldithiolato-Fe complex that plays a significant role in cytoplasmic Fe-handling. Outstanding progress has been made on the metabolism of Fe-prosthetic groups like heme and Fe/S clusters; ionic Fe is the precursor to these "caged" Fe-species and is responsible for the "corrosive chemistry" that characterizes the relationship between Fe and dioxygen. An understanding of how cells suppress this chemistry would make a significant contribution to our eventual elucidation of the molecular basis for the multitude of human pathologies often attributed in part to mismanaged ionic iron.