IRON DEPOSITION AND MOBILIZATION IN FERRITIN

从微生物到人类，铁蛋白在人类免疫系统中起着核心作用。 铁的生物管理 在细胞内，铁是可逆的 以水合氧化铁矿物核心的形式储存在铁蛋白中 在蛋白质里面。 铁蛋白由两种类型的24个亚基组成，H 表观分子量为21，000和19，000的L（重）和L（轻） g/摩尔，组装形成分子量为c.a. 480，000克/摩尔。 这两个亚基被认为具有不同的 促进铁蛋白核心形成的作用。 亚铁氧化酶位点 其催化铁（II）被分子氧氧化， 最近在H亚基上发现了。 的总体目标 拟议的研究是阐明分子机制， 铁蛋白获取和释放铁，特别注意 H和L亚基在这些过程中的作用。 这些机制将是 通过EPR，ENDOR，ESEEM和穆斯堡尔的组合进行了研究 马和羊的光谱学、电化学和动力学研究 脾铁蛋白以及重组H和L人肝铁蛋白， 其定点突变体。 各种EPR可观察到的铁和 在铁沉积的初始阶段形成的自由基物种将 光谱和动力学特征及其位置 在使用突变蛋白质确定的蛋白质结构内， 富含选定的全氘氨基酸的蛋白质。 角色，如果 在铁的氧化和/或还原中，或在铁的氧化和/或还原中， 将检查对蛋白质的氧化损伤。 铁的动力学 将通过氧电极血氧测定法研究氧化和水解， pH统计，分别，和这些过程的速率定律确定。 单核和双核中间体形成的时间顺序 铁和自由基物种将建立快速冷冻淬火EPR 谱 H和L亚基在促进铁离子生成中的作用 氧化和核心成核将探测通过进行 光谱和动力学研究观察到的中间物种 各种定点突变体 生物还原剂与 铁蛋白和铁核心的氧化还原化学的可逆性 将进行电化学研究。 拟议的广泛研究应 从而详细了解铁蛋白作为一种 可逆的铁储存蛋白和进一步我们的知识， 铁生物矿化过程的化学和生物化学 将军

From microorganisms to man, ferritin plays a central role in the biological management of iron. Within the cell, iron is reversibly stored in ferritin in the form of a hydrous ferric oxide mineral core inside the protein. Ferritin consists of 24 subunits of two types, H (heavy) and L (light) of apparent molecular weights 21,000 and 19,000 g/mole, respectively, assembled to form a shell of molecular weight c.a. 480,000 g/mol. The two subunits have been suggested to have different roles in facilitating core formation in ferritin. A ferroxidase site which catalyzes the oxidation of iron(II) by molecular oxygen has recently been discovered on the H-subunit. The overall goal of the proposed research is to elucidate the molecular mechanisms by which ferritin acquires and releases iron with special attention paid to the roles of the H and L subunits in these processes. The mechanisms will be investigated through a combination of EPR, ENDOR, ESEEM and Mossbauer spectroscopy, electrochemistry and kinetic studies of horse and sheep spleen ferritins as well as recombinant H and L human liver ferritins and site-directed mutants thereof. The various EPR observable iron and radical species formed during the initial stages of iron deposition will be characterized spectroscopically and kinetically and their locations within the protein structure determined using mutant proteins and proteins enriched in selected perdeutero amino acids. The role(s), if any, of the observed radicals, in iron oxidation and/or reduction or in oxidative damage to the protein will be examined. The kinetics of iron oxidation and hydrolysis will be studied by oxygen electrode oximetry and pH stat, respectively, and the rate laws for these processes determined. The time sequence of formation of intermediate mononuclear and binuclear iron and radical species will be established by rapid freeze-quench EPR spectroscopy. The functions of H and L subunits in facilitating iron oxidation and core nucleation will be probed by carrying out spectroscopic and kinetic studies of intermediate species observed with various site-directed mutants. The binding of biological reductants to ferritin and the reversibility of the redox chemistry of the iron core will be studied electrochemically. The extensive studies proposed should lead to a detailed understanding of how ferritin functions as a reversible iron storage protein and further our knowledge of the chemistry and biochemistry of iron biomineralization processes in general.