Nagaoka Megumi Hamano, Yamazaki Takeshi, Maitani Tamio
National Institute of Health Sciences, Kamiyoga 1-18-1, Setagaya, 158-8501, Tokyo, Japan.
Biochem Biophys Res Commun. 2002 Sep 6;296(5):1207-14. doi: 10.1016/s0006-291x(02)02067-3.
Vanadium (V) is an essential metal for mammals and has different valence states. In blood, V is bound to serum transferrin (Tf), a glycoprotein which has two metal-binding sites, and carbonate is generally required for the binding. In this study, the binding patterns of V(III), V(IV), and V(V) to human serum Tf (hTf) were analyzed using an HPLC system equipped with an anion-exchange column and directly connected to a high-resolution inductively coupled plasma-mass spectrometer for metal detection (51V). In affinity to hTf, the three ions were ranked V(III)>V(IV)>V(V) in the presence of bicarbonate and V(III) reverse congruent V(IV)>V(V) in the absence. Intermediates in the "open forms" binding to the respective sites were detected at the initial stage. V(IV) and V(V) were bound to the N-lobe site in the "closed form" and "open form," respectively. In the absence of bicarbonate, V ions with respective valence states were bound to hTf in the "open form." In terms of binding to hTf, tri-valent V was most favorable in the presence of bicarbonate.
钒（V）是哺乳动物必需的金属，具有不同的价态。在血液中，钒与血清转铁蛋白（Tf）结合，血清转铁蛋白是一种具有两个金属结合位点的糖蛋白，结合通常需要碳酸盐。在本研究中，使用配备阴离子交换柱并直接连接到用于金属检测（51V）的高分辨率电感耦合等离子体质谱仪的HPLC系统，分析了V(III)、V(IV)和V(V)与人类血清转铁蛋白（hTf）的结合模式。在亲和力方面，在存在碳酸氢盐的情况下，三种离子对hTf的亲和力排序为V(III)>V(IV)>V(V)，而在不存在碳酸氢盐的情况下，V(III)≈V(IV)>V(V)。在初始阶段检测到与各个位点结合的“开放形式”的中间体。V(IV)和V(V)分别以“封闭形式”和“开放形式”与N叶位点结合。在不存在碳酸氢盐的情况下，具有相应价态的钒离子以“开放形式”与hTf结合。就与hTf的结合而言，在存在碳酸氢盐的情况下，三价钒最为有利。
