Das Debashree, Patra Malay, Chakrabarti Abhijit
Biophysics and Structural Genomics Division, Saha Institute of Nuclear Physics, Kolkata, 700064, India.
Eur Biophys J. 2015 Apr;44(3):171-82. doi: 10.1007/s00249-015-1012-2. Epub 2015 Mar 4.
Free heme has toxic effects, for example lipid peroxidation, DNA damage, and protein aggregation. In severe hemolysis, which occurs during pathological states, for example sickle cell disease, ischemia reperfusion, and malaria, levels of free heme increase inside erythrocytes. The purpose of this study was to investigate whether spectrin, the major erythroid cytoskeleton protein, is involved as an acceptor of free heme. We compared the interactions of three heme derivatives, hemin chloride, hematoporphyrin, and protoporphyrin-IX, with dimeric and tetrameric spectrin. The dissociation constants (K d) for binding to spectrin dimer and tetramer were 0.57 and 1.16 µM respectively. Thermodynamic data associated with this binding revealed the binding to be favored by a positive change in entropy. Although molecular docking studies identified the SH3 domain as the unique binding site of these heme derivatives to erythroid spectrin, experimental results indicated a binding stoichiometry of 1 heme attached to both dimeric and tetrameric spectrin, indicating the common self-associating domain to be the unique binding site. We also noticed heme-induced structural changes in the membrane skeletal protein. Erythroid spectrin could thus act as a potential acceptor of heme, particularly relevant under disease conditions.
游离血红素具有毒性作用，例如脂质过氧化、DNA损伤和蛋白质聚集。在病理状态下发生的严重溶血，如镰状细胞病、缺血再灌注和疟疾期间，红细胞内游离血红素水平会升高。本研究的目的是调查血影蛋白（主要的红细胞细胞骨架蛋白）是否作为游离血红素的受体参与其中。我们比较了三种血红素衍生物，即氯化血红素、血卟啉和原卟啉-IX，与二聚体和四聚体血影蛋白的相互作用。与血影蛋白二聚体和四聚体结合时的解离常数（Kd）分别为0.57和1.16 μM。与此结合相关的热力学数据表明，熵的正向变化有利于这种结合。尽管分子对接研究确定SH3结构域是这些血红素衍生物与红细胞血影蛋白的唯一结合位点，但实验结果表明，二聚体和四聚体血影蛋白上均附着1个血红素的结合化学计量比表明，共同的自缔合结构域是唯一的结合位点。我们还注意到血红素诱导的膜骨架蛋白结构变化。因此，红细胞血影蛋白可能作为血红素的潜在受体，在疾病状态下尤为重要。
