Metal ion-dependent binding of gastrin to albumin.
Metal ion-dependent binding of gastrin to albumin.
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DOI：
10.1016/0003-9861(91)90140-e
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发表时间：
1991-12
影响因子：
3.9
通讯作者：
R. Mann;G. Howlett;G. Baldwin
中科院分区：
文献类型：
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作者：
R. Mann;G. Howlett;G. Baldwin
125 I-[Nle 15]胃泌素与从猪血清、猪胃粘膜细胞质和牛血清中纯化的白蛋白的结合已通过共价交联和超离心证实。在Zn ~（2+）、Ni ~（2+）、Cu ~（2+）、Co ~（2+）和Cd ~（2+）的存在下，结合增强，但不存在Ca ~（2+）、Mg ~（2+）或Mn ~（2+）。牛血清白蛋白的结合数据的最佳拟合是用假设两个非等效结合位点的模型获得的。在100 μ mZn ~（2+）或Ni ~（2+）存在下，两个位点对胃泌素的亲和力均增加。在100 μ mZn 2+存在下，观察到的最高缔合常数为2.3 × 105 m − 1。牛和猪血清白蛋白的结合的Zn 2+依赖性的相似性，尽管由Tyr取代His 3，表明N-末端金属离子结合位点不参与。虽然所有的胃泌素亲和力降低了50%，在150毫米NaCl的存在下，锌2+依赖性的结合被保留。因此，我们建议，胃泌素，锌离子，白蛋白的三元复合物可能发挥生理作用，在血清中运输的锌离子和吸收的锌离子从胃肠道的内腔。
Binding of125I-[Nle15]gastrin to albumin purified from porcine serum, from porcine gastric mucosal cytosol, and from bovine serum has been demonstrated by covalent cross-linking and ultracentrifugation. Binding was enhanced in the presence of Zn2+, Ni2+, Cu2+, Co2+, and Cd2+, but not Ca2+, Mg2+, or Mn2+. The best fit to the binding data for bovine serum albumin was obtained with a model assuming two nonequivalent binding sites. The affinity of both sites for gastrin was increased in the presence of 100 μmZn2+or Ni2+ions. The highest association constant observed was 2.3 × 105m−1in the presence of 100 μmZn2+ions. The similarity of the Zn2+-dependence of binding for bovine and porcine serum albumins, despite the replacement of His3 by Tyr, suggested that the N-terminal metal ion-binding site was not involved. Although all gastrin affinities were reduced by 50% in the presence of 150 mmNaCl, the Zn2+-dependence of binding was retained. We therefore propose that the ternary complex of gastrin, Zn2+ions, and albumin may play a physiological role in the serum transport of Zn2+ions and in the uptake of Zn2+ions from the lumen of the gastrointestinal tract.