Lim B C, McArdle H J, Morgan E H
J Comp Physiol B. 1987;157(3):363-71. doi: 10.1007/BF00693363.
Transferrin-receptor interactions and iron uptake were studied in eleven different species of vertebrate animals (3 eutherian mammals, 3 marsupials, 2 reptiles and 1 bird, amphibian and bony fish). In the initial experiments it was shown that the uptake of transferrin-bound iron by immature erythroid cells from marsupial and reptilian species occurs by receptor-mediated endocytosis as in other vertebrate animals. Reticulocytes were incubated with 125I-59Fe-labelled transferrins from heterologous species and the results for iron and transferrin uptake compared with those obtained with the homologous protein. Cells from eutherian mammals were able to take up transferrin and iron from other eutherians and from the bob-tailed lizard but not from marsupials and other submammalian species. With marsupials and reptiles a similar specificity was observed, and the marsupial cells could also utilize chicken transferrin but not vice versa. The results were extended by performing competition experiments in which the cells were incubated with radiolabelled homologous transferrin in the presence of increasing concentrations of non-radioactive heterologous transferrins. From the ability of the heterologous proteins to inhibit uptake of the homologous protein relative association constants (Ka1) for the transferrin-receptor interactions could be calculated. These Ka1 values reflected the patterns observed in the first series of experiments. These studies demonstrate that, although specificity exists in transferrin-receptor interactions throughout the range of vertebrate animals, in several instances reactivity between widely divergent species is also observed. Hence, structural similarities have been maintained throughout evolution. Nevertheless, no evidence of interaction between transferrin and its receptor from the two divisions of the Mammalia, the eutherians and the marsupials, was observed.
在11种不同的脊椎动物（3种真兽类哺乳动物、3种有袋类动物、2种爬行动物、1种鸟类、两栖动物和硬骨鱼）中研究了转铁蛋白 - 受体相互作用及铁摄取。在最初的实验中表明，有袋类和爬行类物种未成熟红细胞对转铁蛋白结合铁的摄取，与其他脊椎动物一样，是通过受体介导的内吞作用进行的。将网织红细胞与来自异源物种的125I - 59Fe标记的转铁蛋白一起孵育，并将铁和转铁蛋白摄取的结果与用同源蛋白获得的结果进行比较。真兽类哺乳动物的细胞能够从其他真兽类动物和短尾蜥蜴摄取转铁蛋白和铁，但不能从有袋类动物和其他低于哺乳动物等级的物种摄取。对于有袋类动物和爬行动物，观察到了类似的特异性，有袋类动物的细胞也可以利用鸡转铁蛋白，但反之则不行。通过进行竞争实验扩展了这些结果，在竞争实验中，细胞在浓度不断增加的非放射性异源转铁蛋白存在下与放射性标记的同源转铁蛋白一起孵育。根据异源蛋白抑制同源蛋白摄取的能力，可以计算转铁蛋白 - 受体相互作用的相对缔合常数（Ka1）。这些Ka1值反映了在第一系列实验中观察到的模式。这些研究表明，尽管在整个脊椎动物范围内转铁蛋白 - 受体相互作用存在特异性，但在一些情况下也观察到了差异很大的物种之间的反应性。因此，在整个进化过程中结构相似性得以保持。然而，未观察到哺乳动物的两个亚纲，即真兽类和有袋类之间转铁蛋白与其受体相互作用的证据。
