Studies of Biological Iron Oxidation

0000989Stahl过渡金属在细胞氧化还原反应中发挥着重要作用。 铁是生物学中最丰富的过渡金属离子，它带来了双重挑战：还原态可能有毒，氧化态在生理条件下非常难溶。 因此，生物系统必须对铁的吸收、运输、储存和使用保持良好的控制。该研究项目旨在研究在生物代谢中发挥关键作用的亚铁氧化酶。 对酿酒酵母的分子生物学和遗传学研究揭示了一种新的真核铁吸收途径的存在。 细胞表面铁还原酶为两种不同的膜转运系统提供亚铁离子。 一种在铁充足的条件下介导铁(II)的吸收，并且还运输其他二价金属离子。 另一种由氧化酶-渗透酶复合物组成，该复合物在低铁条件下运行，并且对铁 (II) 具有很强的选择性。 后者 Fet3p 是一种 72 kDa 膜结合亚铁氧化酶，属于一类被称为多铜氧化酶的酶。 Fet3p 是一种较小的蛋白质，由于缺乏膜结构域的可溶性变体的存在，它似乎更适合详细研究。 该项目将探索 Fet3p 的几个动力学和结构方面，以便深入了解多铜亚铁氧化酶在铁稳态中的作用。 这项研究将包括双氧还原和铁氧化方面的内容，并将为多铜亚铁氧化酶的功能及其在铁代谢中的作用提供基本见解。 用于完成此任务的技术包括不同条件下的停流光谱研究，例如 pH、平衡透析和 NMR 光谱。

0000989StahlTransition metals play an important role in cellular redox reactions. Iron, the most abundant transition metal ion in biology, poses a two-fold challenge: the reduced state can be toxic and the oxidized state is very insoluble under physiological conditions. Consequently, biological systems must maintain fine control over the uptake, transport, storage, and use of iron. This research project is to investigate a ferroxidase enzyme that plays a critical role in biological metabolism. Molecular biological and genetic studies of the organism Saccharomyces cerevisiae revealed the existence of a novel eukaryotic iron uptake pathway. A cell surface ferrireductase provides ferrous ions for two different membrane transport systems. One mediates iron(II) uptake under iron-replete conditions and also transports other divalent metal ions. The other consists of an oxidase-permease complex that operates under low-iron conditions and is very selective for iron(II). This latter one, Fet3p, is a 72 kDa membrane-bound ferroxidase that belongs to a class of enzymes known as multi-copper oxidases. Fet3p is a smaller protein that appears more amenable to detailed study because of the availability of a soluble variant that lacks the membrane domain. This project will explore several kinetic and structural aspects of Fet3p in order to gain mechanistic insights into the role of multicopper ferroxidases in iron homeostasis. This research will include aspects of dioxygen reduction as well as iron oxidation and will provide fundamental insights into the function of multicopper ferroxidases and their role in iron metabolism. Techniques that will be used to accomplish this task include, stopped-flow spectroscopic studies under different conditions such as pH, equilibrium dialysis, and NMR spectroscopy.l