Influence of monovalent cation identity on parvalbumin divalent ion-binding properties
Influence of monovalent cation identity on parvalbumin divalent ion-binding properties
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DOI：
10.1021/bi035890k
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发表时间：
2004-03-16
期刊：
影响因子：
2.9
通讯作者：
Agah, S
中科院分区：
文献类型：
--
作者：
Henzl, MT;Larson, JD;Agah, S
大鼠α -和β -小蛋白具有不同的单价阳离子结合特性[HenzI et al. (2000) Biochemistry 39,5859 -5867]。结合两个Na+或一个K+， a结合一个Na+而不结合K+。Ca2+消除了这些结合事件，表明单价离子占据了EF-hand基序。本研究比较了α和β二价离子在Na+和K+溶液中的亲和力。溶剂阳离子特性严重影响α。在hepes缓冲的5℃NaCl中，Ca2+的宏观结合常数为2.6 × 10(8)和6.4 × 10(7) M-1， Mg2+的宏观结合常数为1.8 × 10(4)和4.3 × 10(3) M-1。在hepes缓冲的KCl中，Ca2+值增加到2.9 × 10(9)和6.6 × 10(8) M-1， Mg2+值增加到2.2 × 10(5)和3.7 × 10(4) M-1。结合数据的蒙特卡罗模拟（采用位点特异性常数并明确考虑Na+结合）得出的K-Na为630 M-1，表明二价离子结合是积极合作的。核磁共振数据表明，唯一的Na+离子占据了CD环。溶剂阳离子同一性对β的影响较小。在Na+中，EF和CD位点的Ca2+常数分别为2.3 × 10(7)和1.5 × 10(6) M-1；Mg2+常数分别为9.2 × 10(3)和1.7 × 10(2) M-1。在K+中，这些值变为3.1 × 10(7)和3.8 × 10(6) M-1，后者变为1.4 × 10(4)和2.9 × 10(2) M-1。这些数据表明，小白蛋白二价离子的亲和力，特别是大鼠α，可以通过增加细胞内Na+水平而显着减弱。
Rat alpha- and beta-parvalbumins have distinct monovalent cation-binding properties [HenzI et al. (2000) Biochemistry 39, 5859-5867]. beta binds two Na+ or one K+, and a binds one Na+ and no K+. Ca2+ abolishes these binding events, suggesting that the monovalent ions occupy the EF-hand motifs. This study compares alpha and beta divalent ion affinities in Na+ and K+ solutions. Solvent cation identity seriously affects alpha. In Hepes-buffered NaCl, at 5 degreesC, the macroscopic Ca2+-binding constants are 2.6 x 10(8) and 6.4 x 10(7) M-1 and the Mg2+ constants, 1.8 x 10(4) and 4.3 x 10(3) M-1. In Hepes-buffered KCl, the Ca2+ values increase to 2.9 x 10(9) and 6.6 x 10(8) M-1 and the Mg2+ values to 2.2 x 10(5) and 3.7 x 10(4) M-1. Monte Carlo simulation of a binding data-employing site-specific constants and explicitly considering Na+ binding-yields a K-Na of 630 M-1 and indicates that divalent ion-binding is positively cooperative. NMR data suggest that the lone Na+ ion occupies the CD loop. Solvent cation identity has a smaller impact on beta. In Na+, the Ca2+ constants for the EF and CD sites are 2.3 x 10(7) and 1.5 x 10(6) M-1, respectively; the Mg2+ constants are 9.2 x 10(3) and 1.7 x 10(2) M-1. In K+, these values shift to 3.1 x 10(7) and 3.8 x 10(6) M-1 and the latter to 1.4 x 10(4) and 2.9 x 10(2) M-1. These data suggest that parvalbumin divalent ion affinity, particularly that of rat alpha, can be significantly attenuated by increased intracellular Na+ levels.