Harris D C
Biochemistry. 1978 Jul 25;17(15):3071-8. doi: 10.1021/bi00608a020.
The transfer of iron between horse spleen [55Fe]ferritin and human apotransferrin or [59Fe]transferrin in homogeneous solution was investigated. Transfer between the two proteins in the presence of citrate, ATP, or ascorbate occurs in both direction, but the net flow is always from ferritin to transferrin. Ferritin which is ca. 1/3 to 1/2 saturated with iron appears to be most reactive. Chemically prepared apoferritin does not accept iron from diferric transferrin. Citrate-mediated transfer of iron from ferritin to apotransferrin is first order with respect to ferritin, zero order with respect to transferrin, and has a complex dependence upon citrate concentration. Direct transfer of iron from native or reconstituted ferritin to apotransferrin in the absence of any identifiable mediating agent was observed to occur at about half the rate attained in the presence of 1 mM citrate. No transfer of iron between the two proteins occurs across a dialysis membrane in the absence of a mediating agent. No binding of transferrin and ferritin to each other was demonstrable. One possible explanation for these observations is that iron from the core of ferritin is in equilibrium with iron near the outer surface of the protein, where the metal would be available to transferrin.
研究了在均相溶液中，铁在马脾[55Fe]铁蛋白与人脱铁转铁蛋白或[59Fe]转铁蛋白之间的转移情况。在柠檬酸盐、ATP或抗坏血酸盐存在的情况下，两种蛋白质之间的铁转移在两个方向上都能发生，但净流动总是从铁蛋白流向转铁蛋白。铁饱和度约为1/3至1/2的铁蛋白似乎反应性最强。化学制备的脱铁铁蛋白不能从双铁转铁蛋白接受铁。柠檬酸盐介导的铁从铁蛋白向脱铁转铁蛋白的转移，对铁蛋白而言是一级反应，对转铁蛋白而言是零级反应，并且对柠檬酸盐浓度有复杂的依赖性。在没有任何可识别的介导剂的情况下，观察到天然或重组铁蛋白中的铁直接向脱铁转铁蛋白的转移速率约为在1 mM柠檬酸盐存在下所达到速率的一半。在没有介导剂的情况下，两种蛋白质之间的铁不会通过透析膜发生转移。未证明转铁蛋白和铁蛋白之间存在相互结合。对这些观察结果的一种可能解释是，来自铁蛋白核心的铁与蛋白质外表面附近的铁处于平衡状态，在那里金属可被转铁蛋白利用。
