Ishitani K, Listowsky I
J Biol Chem. 1975 Jul 25;250(14):5446-9.
Horse spleen ferritin was fractionated into its constituent isoferritins by isoelectric focusing. Separated isoferritins were stable and showed no tendency to redistribute when re-examined by analytical gel focusing. All of the isoferritins were immunologically indistinguishable when tested with antibodies raised against unfractionated horse spleen ferritin. The separated isoferritins also had similar conformations as determined by circular dichroism. Iron distribution studies, however, revealed a wide disparity among the isoferritins. The most acidic components had the lowest iron content but the iron content did not vary systematically throughout the isoferritin spectrum. Natural apoferritin, isolated from the ferritin by density gradient centrifugation, focused exclusively as the acidic moieties, whereas apoferritin prepared by reduction of native ferritin exhibited a banding pattern similar to that of unfractionated ferritin. The subunit structure of the isoferritins was examined by gel electrophoresis in sodium dodecyl sulfate or acidic urea systems. Multiple subunit types were demonstrated by both methods. The relative proportion of these subunit types varied progressively through the isoferritin spectrum. This difference in subunit population appears to be the basis for much of the structural heterogeneity in the apoferritin shells.
通过等电聚焦将马脾铁蛋白分离成其组成的异铁蛋白。分离出的异铁蛋白是稳定的，当通过分析凝胶聚焦重新检测时，没有重新分布的趋势。当用针对未分级的马脾铁蛋白产生的抗体进行测试时，所有异铁蛋白在免疫上无法区分。通过圆二色性测定，分离出的异铁蛋白也具有相似的构象。然而，铁分布研究揭示了异铁蛋白之间存在很大差异。最酸性的组分铁含量最低，但在整个异铁蛋白谱中铁含量并没有系统地变化。通过密度梯度离心从铁蛋白中分离出的天然脱铁铁蛋白，仅聚焦为酸性部分，而通过还原天然铁蛋白制备的脱铁铁蛋白呈现出与未分级铁蛋白相似的条带模式。通过在十二烷基硫酸钠或酸性尿素系统中进行凝胶电泳来检查异铁蛋白的亚基结构。两种方法都证明了多种亚基类型。这些亚基类型的相对比例在整个异铁蛋白谱中逐渐变化。亚基群体的这种差异似乎是脱铁铁蛋白外壳中许多结构异质性的基础。
