Esmann Mikael, Fedosova Natalya U
Department of Biophysics, University of Aarhus, Ole Worms Allé 185, 8000, Aarhus, Denmark.
Eur Biophys J. 2004 Dec;33(8):683-90. doi: 10.1007/s00249-004-0411-6. Epub 2004 May 15.
Nucleotide binding affinity to Na,K-ATPase is reduced by a number of anions such as nitrate and perchlorate in comparison with affinity in the presence of chloride (all with sodium as the cation). The reduction correlates with the position of these anions in the Hofmeister series. Transient kinetic experiments using the fluorescent dye eosin-which binds to the nucleotide site of the Na,K-ATPase-show that simultaneous anion binding, exemplified with nitrate, and eosin binding is possible. The effect of nitrate on eosin binding is reflected in a decreased binding-rate constant and an increased dissociation rate constant, leading to a decreased equilibrium binding constant for eosin. Since eosin binding is analogous with nucleotide binding to Na,K-ATPase, the results suggest the simultaneous presence of nucleotide and anion binding sites.
与存在氯化物（均以钠为阳离子）时的亲和力相比，硝酸盐和高氯酸盐等多种阴离子会降低核苷酸与钠钾-ATP酶的结合亲和力。这种降低与这些阴离子在霍夫迈斯特序列中的位置相关。使用与钠钾-ATP酶的核苷酸位点结合的荧光染料曙红进行的瞬态动力学实验表明，以硝酸盐为例，阴离子的同时结合和曙红的结合是可能的。硝酸盐对曙红结合的影响表现为结合速率常数降低和解离速率常数增加，导致曙红的平衡结合常数降低。由于曙红结合与核苷酸与钠钾-ATP酶的结合类似，结果表明存在核苷酸和阴离子结合位点。
