CALORIMETRIC STUDIES OF THE BINDING OF FERRIC IONS TO HUMAN SERUM TRANSFERRIN
CALORIMETRIC STUDIES OF THE BINDING OF FERRIC IONS TO HUMAN SERUM TRANSFERRIN
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DOI：
10.1021/bi00087a019
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发表时间：
1993-09-14
期刊：
影响因子：
2.9
通讯作者：
BRANDTS, JF
中科院分区：
文献类型：
--
作者：
LIN, LN;MASON, AB;BRANDTS, JF
用超灵敏滴定量热法研究了氨三乙酸螯合三价铁离子与人血清转铁蛋白（hTF）的结合。在存在和不存在协同碳酸氢根阴离子的情况下进行研究。发现hTF的C-位点甚至在加入三价铁离子之前能够在结合位点弱结合碳酸氢根（K为250 M-1，Δ H为-8 kcal），尽管这在N-位点没有发生相同的程度。当发生碳酸氢根离子的预插入时，随后三价铁离子可以非常快速地结合到C位点。虽然螯合的三价铁离子可以在快速反应中弱结合到N-位点，但碳酸氢根离子的插入随后在缓慢的吸热反应中发生。在不存在碳酸氢盐的情况下，三价铁离子与两个位点的结合是快速可逆的，但是一旦碳酸氢盐插入金属结合位点，由于释放三价铁离子所需的长时间，三价铁离子与两个位点的结合就变得长时间动力学受控。估计热量的结合到每个网站，表观结合常数，结合的热容量是为不同的解决方案的条件。将来自该研究的结果与卵转铁蛋白的早期结果（Lin，L. N.，梅森A. B.，伍德沃思河C.的方法，& Brandts，J. F.（1991）Biochemistry 30，11660-11669），其中注意到主要差异和一些相似性。
The binding of ferric ions, chelated with nitrilotriacetate, to human serum transferrin (hTF) has been studied using ultrasensitive titration calorimetry. Studies were done in both the presence and the absence of the synergistic bicarbonate anion. It was found that the C-site of hTF is capable of weakly binding bicarbonate (K of 250 M-1, DELTAH of -8 kcal) at the binding site even before ferric ion is added, although this does not happen to the same extent at the N-site. When preinsertion of the bicarbonate ion occurs, then ferric ion can subsequently bind very quickly to the C-site. Although the chelated ferric ion can bind weakly to the N-site in a fast reaction, the insertion of the bicarbonate ion occurs subsequently in a slow endothermic reaction. Binding of ferric ion to both sites is quickly reversible in the absence of bicarbonate but becomes kinetically controlled for long periods of time once bicarbonate has inserted into the metal-binding site due to the long time required for release of ferric ion. Estimates of the heats of binding to each site, apparent binding constants, and heat capacities of binding are made for different sets of solution conditions. Results from this study are compared to earlier results with ovotransferrin (Lin, L.-N., Mason, A. B., Woodworth, R. C., & Brandts, J. F. (1991) Biochemistry 30, 11660-11669), with major differences and some similarities noted.