MEASUREMENT OF NON-SYNERGISTIC ANION BINDING TO TRANSFERRIN BY ELECTRON-PARAMAGNETIC-RES DIFFERENCE SPECTROSCOPY
MEASUREMENT OF NON-SYNERGISTIC ANION BINDING TO TRANSFERRIN BY ELECTRON-PARAMAGNETIC-RES DIFFERENCE SPECTROSCOPY
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DOI：
10.1021/ja00385a036
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发表时间：
1982-01-01
影响因子：
15
通讯作者：
CHASTEEN, ND
中科院分区：
文献类型：
--
作者：
FOLAJTAR, DA;CHASTEEN, ND
用EPR差谱法研究了盐对人血清转铁蛋白2铁中心的影响。随着盐浓度的增加，EPR谱的变化源于阴离子与一类新的位点的结合，这些位点与协同阴离子碳酸酯所占据的位点不同。这些非协同阴离子与蛋白质的相互作用是非常不寻常的，因为阴离子以强的正协同性成对结合。提出了一个描述阴离子与该多位点蛋白结合的数学模型。从这个模型和对差铁和2个单铁转铁蛋白的测量，可以推断出4个阴离子与蛋白质结合，每个结构域2个。各结构域阴离子结合的表观总结合常数为硫氰酸盐>高氯酸盐> PPi > ATP > CO- .mchgt。四氟硼酸盐，Pi， AMP, Fl-，硫酸盐和碳酸氢盐。在阴离子与蛋白质相互作用的强度上，上述序列与溶性序列相似。生理上相关的非协同阴离子如Cl-、ATP和PPi与转铁蛋白的结合可能对影响这一重要蛋白的铁结合特性很重要。讨论了阴离子结合、铁结合和铁释放动力学之间的关系。
The effects of salts on the 2 Fe centers of human serum transferrin were investigated by EPR difference spectroscopy. The change in the EPR spectrum with increasing salt concentration arises from the binding of anions to a novel class of sites that are distinct from those occupied by the synergistic anion carbonate. The interaction of these nonsynergistic anions with the protein is very unusual in that the anions bind pairwise with strong positive cooperativity. A mathematical model describing anion binding to this multisited protein is presented. From this model and from measurements on diferric and the 2 monoferric transferrins, it is inferred that 4 anions bind to the protein, 2 in each domain. The values of the apparent overall association constant for anion binding in each domain are presented and follow the sequence thiocyanate > perchlorate > PPi > ATP > CO- .mchgt. tetrafluoroborate, Pi, AMP, Fl-, sulfate, and bicarbonate. The above sequence parallels the lyotropic series for the strength of anion interactions with proteins. The binding of physiologically relevant nonsynergistic anions such as Cl-, ATP, and PPi to transferrin may be important in influencing the Fe binding properties of this important protein. The relationships between anion binding, Fe binding, and the kinetics of Fe release are discussed.