Moutafchiev D A, Sirakov L M, Naidu A S
Department of Biochemistry, Medico-Biological Institute Medical Academy, Sofia, Bulgaria.
J Dairy Sci. 1991 Sep;74(9):2959-64. doi: 10.3168/jds.S0022-0302(91)78481-6.
The binding of mouse and rabbit transferrins to lactating mouse mammary epithelial cells was tested in a 59Fe-protein-binding assay. The homologous and heterologous binding was slow during the first 30 min, after which the uptake steadily increased. In ligand concentration-dependent saturation studies, the heterologous rabbit protein showed a high degree of binding and required approximately 9.7 ng of ligand to saturate approximately 2 x 10(6) cells. The homologous mouse protein demonstrated a low degree of binding and failed to demonstrate saturation at the above ligand concentration. Scatchard plot for homologous binding data was nonlinear and implied a low (1.08 x 10(-10) M) and a high (1.82 x 10(-9) M) affinity interaction mechanism. However, the plot for heterologous binding was linear and characterized by one high affinity (1.0 x 10(-9) M) binding interaction. A total of 11,000 and 19,600 binding sites per cell were estimated for mouse and rabbit proteins, respectively. These data suggest a binding crossreactivity between mouse and rabbit transferrins. A high affinity binding mechanism seems to be conserved in proteins from both species; however, an additional low affinity binding was present only in the homologous system.
在一项⁵⁹Fe - 蛋白质结合试验中，检测了小鼠和兔转铁蛋白与泌乳期小鼠乳腺上皮细胞的结合情况。在最初30分钟内，同源和异源结合都很缓慢，之后摄取量稳步增加。在配体浓度依赖性饱和研究中，异源兔蛋白显示出高度结合，使约2×10⁶个细胞饱和大约需要9.7 ng配体。同源小鼠蛋白显示出低度结合，在上述配体浓度下未能显示饱和。同源结合数据的Scatchard图呈非线性，表明存在低亲和力（1.08×10⁻¹⁰ M）和高亲和力（1.82×10⁻⁹ M）相互作用机制。然而，异源结合的图是线性的，其特征为一种高亲和力（1.0×10⁻⁹ M）结合相互作用。估计小鼠和兔蛋白每个细胞分别有11,000个和19,600个结合位点。这些数据表明小鼠和兔转铁蛋白之间存在结合交叉反应性。高亲和力结合机制似乎在两个物种的蛋白质中都保守；然而，额外的低亲和力结合仅存在于同源系统中。
