Voegele Andreas F, Jerković Lidija, Wellenzohn Bernd, Eller Patricia, Kronenberg Florian, Liedl Klaus R, Dieplinger Hans
Vitateq Biotechnology GmbH, Innsbruck, Austria.
Biochemistry. 2002 Dec 10;41(49):14532-8. doi: 10.1021/bi026513v.
Human plasma afamin, the fourth member of the albumin gene family, is shown to be a specific binding protein for vitamin E. A radio ligand-binding assay followed by Scatchard and Hill analysis are used to show that afamin has a binding affinity for both alpha-tocopherol and gamma-tocopherol, two of the most important forms of vitamin E, in vitro. The binding-dissociation constant was determined to be 18 microM, indicating that afamin plays a role as vitamin E carrier in body fluids such as human plasma and follicular fluid under physiological conditions. Additionally, we demonstrate that afamin has multiple binding sites for both alpha- and gamma-tocopherol. Due to the large binding capacity of afamin for vitamin E, it might take over the role of vitamin E transport in body fluids under conditions where the lipoprotein system is not sufficient for vitamin E transport. To confirm the experimental results, we performed homology modeling and docking calculations on the predicted tertiary structure, which showed coincidence between calculated and in vitro results.
人血浆α-甲胎蛋白是白蛋白基因家族的第四个成员，被证明是维生素E的特异性结合蛋白。采用放射性配体结合试验，随后进行Scatchard和Hill分析，以表明α-甲胎蛋白在体外对α-生育酚和γ-生育酚（维生素E的两种最重要形式）具有结合亲和力。结合解离常数测定为18微摩尔，表明在生理条件下，α-甲胎蛋白在诸如人血浆和卵泡液等体液中作为维生素E载体发挥作用。此外，我们证明α-甲胎蛋白对α-和γ-生育酚都有多个结合位点。由于α-甲胎蛋白对维生素E具有较大的结合能力，在脂蛋白系统不足以进行维生素E转运的情况下，它可能会接管体液中维生素E转运的作用。为了证实实验结果，我们对预测的三级结构进行了同源建模和对接计算，结果显示计算结果与体外实验结果相符。
