Studies of anion binding by transferrin using carbon-13 nuclear magnetic resonance spectroscopy.
Studies of anion binding by transferrin using carbon-13 nuclear magnetic resonance spectroscopy.
复制标题
使用碳 13 核磁共振波谱研究转铁蛋白与阴离子的结合。
DOI：
10.1021/bi00515a031
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发表时间：
1981
期刊：
影响因子：
2.9
通讯作者：
J. Cohen
中科院分区：
文献类型：
--
作者：
J. Zweier;J. B. Wooten;J. Cohen
在68兆赫下研究了转铁蛋白与富13c -en （bi）碳酸盐结合的Co3+和Fe3+配合物。获得了金属结合的机制、金属与阴离子结合位点的空间关系、阴离子的电离状态、阴离子的蛋白质连接以及两种阴离子结合位点性质的差异等方面的信息。Co3+ 2配合物的光谱包含一个因不交换阴离子而产生的双重共振和三个因交换阴离子而产生的共振。非交换阴离子结合在B位，根据其化学位移值和pH值，我们得出它是碳酸盐。交换阴离子结合在A位点，它们被分配到结合的碳酸氢盐和蛋白质-碳氨基加合物上。在Fe3+ 2配合物的光谱中，没有观察到与特定结合阴离子对应的共振，因为这些13C共振通过与顺磁性Fe3+相互作用而展宽，无法检测到。在先前的一项25 MHz的研究中，同样观察到13C共振被拓宽到无法检测，但由于人血清中的铁转运蛋白transferrin有两个金属结合位点，只有在同时结合立体化学上合适的阴离子时，每个金属结合位点才能结合铁离子（Warner & Weber, 1953; Aisen etal ., 1967; Price & Gibson, 1972; Bates & Schlabach, 1975）。金属结合位点能够结合多种二价和三价金属离子，包括Co3+和Cu2+(Aasa & Aisen, 1968; Aisen etal ., 1969; Zweier & Aisen, 1977)。阴离子在Fe3+结合和释放中的作用一直受到质疑，有证据表明，将铁传递到网状细胞的机制涉及网状细胞对结合阴离子的攻击（Aisen & Leibman, 1973）。已经进行了许多研究来确定结合金属和阴离子的空间关系（Harris etal ., 1974; Harris & Aisen, 1975b; Najarían etal ., 1978）。最近有研究表明，Cu2+-转铁蛋白-草酸盐配合物中的阴离子直接与金属结合（Zweier etal ., 1979）。然而，阴离子是否与Fe3+结合还没有确定
Co3+ and Fe3+ complexes of transferrin with bound 13C-en-riched (bi) carbonate have been studied at 68 MHz. Infor-mation has been obtained about the mechanism of metal binding, the spatial relationship of the metal and the anion binding sites, theionization state of the anion, the protein ligation of the anion, and differencesin the properties of the two anion binding sites. The spectrum of the Co3+ 2 complex contains a doublet resonance due to nonexchanging anion and three resonances due to exchanging anions. The nonex-changing anion is bound at the B site, and on the basis of its chemical shift value and its pH behavior we concluded that it is carbonate. The exchanging anions are bound at the A site, and they are assigned to bound bicarbonate and a protein-carbamino adduct. In thespectra of the Fe3+ 2 complex, no resonances corresponding to specifically bound anion are observed since these 13C resonances are broadened beyond detection by interaction with the paramagnetic Fe3+. In a previous study at 25 MHz, it was similarly observed that the 13C resonances were broadened beyond detection, but due toTransferrin, the iron-transport protein of human serum, has two metal binding sites, each of which binds a ferric ion only when a stereochemically suitable anion is concomitantly bound (Warner & Weber, 1953; Aisen et al., 1967; Price & Gibson, 1972; Bates & Schlabach, 1975). The metal binding sites are capable of binding a number of di-and trivalent metal ions, including Co3+ and Cu2+(Aasa & Aisen, 1968; Aisen et al., 1969; Zweier & Aisen, 1977). The role of the anion in Fe3+ binding and release has been questioned, and there is evidence that the mechanism for the delivery of iron to the reticulocyte involves an attack by the reticulocyte on the bound anion (Aisen & Leibman, 1973). A number of studies have been performed to determine the spatial relationship of the bound metal and anion (Harris et al., 1974; Harris & Aisen, 1975b; Najarían et al., 1978). Recently, it has been demonstrated that the anion inthe Cu2+-transferrin-oxalate complex is directly bound to the metal (Zweier et al., 1979). However, it has not been determined if the anion is bound to Fe3+ in the