Longano S C, Knesel J, Howlett G J, Baldwin G S
Melbourne Tumour Biology Branch, Ludwig Institute for Cancer Research, Royal Melbourne Hospital, Victoria, Australia.
Arch Biochem Biophys. 1988 Jun;263(2):410-7. doi: 10.1016/0003-9861(88)90653-4.
The sedimentation behavior of 125I-labeled gastrin has been studied as a function of Fe3+ ion concentration and pH. Both sedimentation velocity and sedimentation equilibrium experiments indicated that high-molecular-weight Fe3+-gastrin complexes were formed at pH 5.0 and pH 7.4. Self-association of gastrin alone was observed at pH values below 5.0. 125I-labeled gastrin bound to human serum apotransferrin at pH 7.4. Scatchard analysis of the gastrin-apotransferrin complex gave a Kd of approximately 6.4 microM at 37 degrees C, with two binding sites per molecule of apotransferrin. No significant binding of gastrin to diferric transferrin was observed under the same conditions. The binding of gastrin to apotransferrin was inhibited by NaCl. The results are consistent with the hypothesis that gastrin and transferrin act synergistically in the uptake of dietary iron by the gastrointestinal tract.
研究了¹²⁵I标记胃泌素的沉降行为与Fe³⁺离子浓度和pH的关系。沉降速度和沉降平衡实验均表明，在pH 5.0和pH 7.4时形成了高分子量的Fe³⁺-胃泌素复合物。在pH值低于5.0时观察到胃泌素自身缔合。¹²⁵I标记的胃泌素在pH 7.4时与人血清脱铁转铁蛋白结合。对胃泌素-脱铁转铁蛋白复合物进行Scatchard分析，在37℃时得到的解离常数Kd约为6.4 μM，每个脱铁转铁蛋白分子有两个结合位点。在相同条件下未观察到胃泌素与双铁转铁蛋白有明显结合。胃泌素与脱铁转铁蛋白的结合受到NaCl的抑制。这些结果与胃泌素和转铁蛋白在胃肠道摄取膳食铁过程中协同作用的假说一致。
