Joshi J G, Sczekan S R, Fleming J T
Department of Biochemistry, University of Tennessee, Knoxville 37996-0840.
Biol Trace Elem Res. 1989 Jul-Sep;21:105-10. doi: 10.1007/BF02917242.
Binding of nonferrous metal ions to ferritin was compared to that of the phosphate-free or phosphate containing synthetic iron cores. The Scatchard plots for the synthetic cores reveal a high affinity site for Cd, Zn, Be, and Al, with KD in the range 10(-5)-10(-7) M. Preloading the cores with phosphate increased the number of metal ions bound without altering the KD. The metal ions with smaller ionic radii (Be, Al) were bound in larger numbers than those with larger ionic radii (Cd, Zn). Ferritin isolated from soybean (Glycina max), horse spleen, and rat liver bound the metal ions in amounts larger than predicted from their iron core. Whereas the iron cores and their nonferrous metal ion complexes were insoluble, those in the protein shell remained in solution. Thus apoferritin precipitated with lower concentrations of aluminum than did holoferritin. Also, Al bound to apoferritin reduced the rate of iron loading into the protein.
将有色金属离子与铁蛋白的结合情况与不含磷酸盐或含磷酸盐的合成铁芯的结合情况进行了比较。合成铁芯的斯卡查德图显示，镉、锌、铍和铝存在高亲和力位点，解离常数（KD）在10^(-5)-10^(-7) M范围内。用磷酸盐预加载铁芯会增加结合的金属离子数量，而不会改变KD。离子半径较小的金属离子（铍、铝）的结合数量比离子半径较大的金属离子（镉、锌）更多。从大豆（大豆属）、马脾和大鼠肝脏中分离出的铁蛋白结合金属离子的量比根据其铁芯预测的量要大。虽然铁芯及其有色金属离子络合物不溶，但蛋白质外壳中的络合物仍留在溶液中。因此，脱铁铁蛋白比全铁铁蛋白在更低的铝浓度下沉淀。此外，与脱铁铁蛋白结合的铝降低了铁加载到蛋白质中的速率。
