MECHANISM OF IRON REMOVAL FROM TRANSFERRIN

从转铁蛋白中去除铁的机制

• 批准号: 3233853
• 负责人: WESLEY R HARRIS
• 金额: $ 5.16万
• 依托单位: UNIVERSITY OF MISSOURI-ST. LOUIS
• 依托单位国家: 美国
• 财政年份: 1984
• 资助国家: 美国
• 起止时间: 1984-08-06 至 1991-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/3233853
• 关键词: aminoacid; aminophosphonate; bicarbonates; catechols; hydroxamate; iron disorder; iron metabolism; iron storage disorder; ligands; phosphonate; polyphosphates; radiotracer; sickle cell anemia; thalassemia; transferrin

Serum transferrin is the protein responsible for the transport of iron between sites of assimilation, utilization, and storage. The mechanism by which low molecular weight chelating agents remove ferric ion from this protein is still not clearly understood. Characterization of the iron removal process is of fundamental important for understanding intracellular iron release and for the development of new chelating agents for the treatment of iron overload that results from the chronic transfusion therapy associated with anemias such as -thalassemia. Conflicting mechanisms have been proposed to explain the saturation kinetics observed with catecholate, phosphate, phosphonate, and hydroxamate ligands. During the initial period of this project, it was shown that neither mechanism in its simplest form is correct, and a modified rate law was proposed which includes two parallel pathways for iron removal. The purpose of the proposed research is to delineate the mechanistic steps associated with each pathway. These studies will also determine the kinetic differences between the two transferrin binding sites. Iron removal kinetics for ferric ion will be followed using visible spectrophotometry. Rapid scanning spectrophotometry will be used to follow the donation of ferric ion to apotransferrin and the reactions of bicarbonate with ternary transferrin complexes containing a phosphonate synergistic ion. Kinetic studies on the removal of trivalent A1 and In from transferrin will be included, using the uv band at 295 nm to follow the reaction. These metal ions are respectively more inert and more labile than ferric ion, and thus one should observe shifts in reaction rates for steps that involve breaking of iron-ligand bonds. Cyclic voltammetry with chemically modified electrodes appears to distinguish two forms of ferric transferrin which differ in their rate of reduction. This technique will be used to directly monitor conformation changes of ferric transferrin as a function of pH, temperature, and added salts. High added salts. High field 31p nmr will be used to characterize the interactions of the phosphonates with both apo- and diferric transferrin. The objective is to identify the purported mixed-ligand intermediates involved in iron removal by these ligands, characterize the ligand binding site, and estimate its distance from the ferric ion.

血清转铁蛋白是一种蛋白质，负责运输 铁之间的网站同化，利用和存储。 的 低分子量螯合剂 从该蛋白质中除去铁离子仍然不清楚。 对除铁过程的表征是重要的 这对于理解细胞内铁的释放和 新型螯合剂的研制 长期输血治疗导致的超负荷 与贫血相关的疾病，如地中海贫血。 已经提出了解释这种现象的机制， 用儿茶酚盐，磷酸盐， 膦酸盐和异羟肟酸盐配体。 初创时期 在这个项目中，结果表明， 最简单的形式是正确的，并提出了一个修正的速率定律 其包括两个平行的除铁通道。 的 拟议研究的目的是描绘机制 与每一条路径相关的步骤。 这些研究还将 确定两种转铁蛋白之间的动力学差异 结合位点。 将使用可见光光度计跟踪铁离子的铁去除动力学。 分光光度法 快速扫描分光光度法将是 用于跟踪铁离子对脱铁转铁蛋白的贡献， 碳酸氢盐与三元转铁蛋白复合物的反应 含有膦酸盐增效离子。 的动力学研究 将包括从转铁蛋白中除去三价A1和In， 使用295 nm的UV带跟踪反应。 这些金属 离子分别比铁离子更惰性和更不稳定， 因此应该观察到对于 涉及铁-配体键的断裂。 出现了化学修饰电极的循环伏安法 为了区分铁转铁蛋白的两种形式， 减少的速度。 这项技术将用于直接监测 铁转铁蛋白的构象变化作为pH的函数， 温度，和添加的盐。 高添加盐。 高场31 p NMR将用于表征 具有脱辅基和二铁转铁蛋白的膦酸盐。 的 目的是鉴定所谓的混合配体中间体 通过这些配体参与铁去除，表征配体 结合位点，并估计其与铁离子的距离。