IRON-APOFERRITIN--EFFECT & STRUCTURE OF SUBUNIT DIMERS

铁蛋白是一种以生物可利用形式储存铁的金属蛋白， 克服了生命系统中铁的低溶解度（10-18M）。 小号 高等生物体的所有细胞中都存在大量铁蛋白，提供铁 用于 DNA 合成、电子传递和氧活化的蛋白质 和运输，而大量发生在铁的特殊细胞中 存储，例如肝脏、脾脏和胚胎红细胞。 病理性的 当铁储备不足或过载时，就会出现这种情况。 叠加在高度保守的序列上的是细胞特异性特征 可能与功能和/或相关的铁蛋白序列和结构 监管。 铁蛋白结构可以通过细胞质进一步修饰 导致功能变化的组件。 我们最近发现了这样的 变化：铁蛋白亚基二聚体交联，翻译后 铁蛋白的修饰，似乎可以调节铁蛋白的铁含量 体内。 此次观测是首次发现的自然结构 与铁蛋白的铁储存功能相关的修饰，对我们来说 知识。 与 F2DNB 交联可复制该效果。 结构性 交联的要求（不是-S-S）将按以下条款进行检查 连接氨基酸、序列和亚基的身份 限制（通过序列分析和与已知亚基的比较 序列），被敏感单克隆抗体识别的序列 交联的存在，交联形成的生物合成途径 （H-3-亮氨酸脉冲标记）和可能影响的细胞质成分 交联（转肽酶？抗坏血酸？）。 从羔羊中克隆铁蛋白 cDNA 脾脏或其他来源将被准备并用于获取有关 与交联相关的铁蛋白 mRNA 的序列和调控。 的 交联的功能效果将被测量为 对铁吸收和释放的交联敏感单克隆抗体 体外以及交联对铁-蛋白质相互作用的影响， 使用 X 射线观察磷酸盐-铁-蛋白质相互作用和铁核心结构 吸收光谱（EXAFS 和 XANES）。 结果将很重要 了解铁的病理改变的分子基础 存储，例如缺铁性贫血、血色素沉着症、地中海贫血等 肝硬化，以及了解细胞特异性之间的关系 蛋白质结构、细胞质修饰剂和调控的特征 的功能。

Ferritin, a metalloprotein which stores iron in a bioavailable form, overcomes the low solubility (10-18M) of iron in living systems. Small amounts of ferritin occur in all cells of higher organisms, providing iron for proteins of DNA synthesis, electron transport, and oxygen activation and transport, while large amounts occur in specialized cells of iron storage, e.g. liver, spleen, and red cells of embryo. Pathological conditions occur when iron stores are low or are overloaded. Superimposed on a highly conserved sequence are cell-specific features of ferritin sequence and structure which may relate to function and/or regulation. Ferritin structure could be further modified by cytoplasmic components leading to functional changes. We have recently identified such a change: ferritin subunit dimer crosslinks, a posttranslational modification of ferritin, appear to regulate the iron content of ferritin in vivo. The observation is the first identified, natural structural modification related to the iron storage function of ferritin, to our knowledge. Crosslinking with F2DNB replicates the effect. The structural requirements for crosslinks (which are not -S-S) will be examined in terms of the identity of the linked amino acids, the sequence and subunit restrictions (by sequence analysis and comparison to known subunit sequences), the sequences recognized by monoclonal antibodies sensitive to the presence of crosslinks, the biosynthetic pathway of crosslink formation (H-3-leucine pulse labeling) and cytoplasmic components which may influence crosslinks (transpeptidases? ascorbate?). Cloned ferritin cDNA from lamb spleen or other sources will be prepared and used to gain information about the sequence and regulation of ferritin mRNA related to crosslinks. The functional effect of crosslinks will be measured as the effect of crosslink-sensitive monoclonal antibodies on iron uptake and release in vitro and as the effect of crosslinks on Fe-protein interactions, phosphate-Fe-protein interactions, and iron core structure, using X-ray absorption spectroscopy (EXAFS and XANES). The results will be important in understanding the molecular basis for pathologically altered iron storage, e.g. iron deficiency anemia, hemochromatosis, thalassemia, and cirrhosis, as well as understanding the relationship among cell-specific features of protein structure, cytoplasmic modifying agents, and regulation of function.