COMPARISON OF THE ZINC-BINDING DOMAINS IN THE 7S NERVE GROWTH-FACTOR AND THE ZINC INSULIN HEXAMER
COMPARISON OF THE ZINC-BINDING DOMAINS IN THE 7S NERVE GROWTH-FACTOR AND THE ZINC INSULIN HEXAMER
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DOI：
10.1021/bi00545a017
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发表时间：
1980-01-01
期刊：
影响因子：
2.9
通讯作者：
QUIEL, E
中科院分区：
文献类型：
--
作者：
DUNN, MF;PATTISON, SE;QUIEL, E
发色团二价金属离子螯合剂2，2“，2”-三联吡啶（Terpy）被用作动力学和光谱探针，以研究小鼠7S神经生长因子蛋白（7S NGFn）和锌-胰岛素六聚体（In）6（Zn 2+）2中的锌结合结构域。停流快速混合动力学的时间过程中的螯合和去除锌2+从这两个锌金属蛋白激素是显着的双相。每个反应的快速相是2级整体：1级在Terpy和1级在蛋白质结合的Zn 2+。虽然与慢相相关联的光谱变化对应于每g原子的Zn 2+吸收1摩尔的Terpy，但慢相是一个一阶过程（Terpy中的零阶）。的浓度依赖性和光谱的变化是一致的一个共同的反应机制，这两种蛋白质;快速阶段涉及的单（Terpy）-Zn（II）-蛋白质复合物的形成在每个锌网站，和缓慢阶段涉及的速率限制解离的Terpy结合的Zn 2+从蛋白质，其次是快速协调的第二个Terpy分子和形成的双（Terpy）-Zn（II）复合物。相比之下，Terpy与羧肽酶A和B、碳酸酐酶、嗜热菌蛋白酶和马肝醇脱氢酶的反应都非常缓慢（t1/2 [半衰期]为数小时至数天）。在每种情况下，时间过程由单个指数描述。（In）6（Zn 2+）2的高分辨率X射线结构为双相时间过程提供了令人满意的结构原理。2个Zn 2+中的每一个都是六配位的。其中三个配体是水分子;其余3个是His-B10的咪唑基部分。基于这种结构信息，反应的快速阶段涉及三齿三联三联吡啶置换3个水分子。7S NGFn和（In）6（Zn 2+）2与Terpy反应之间的惊人相似性表明7S NGFn和（In）6（Zn 2+）2的Zn结合结构域中存在结构相似性。
The chromophoric divalent metal ion chelator 2,2'',2"-terpyridine (Terpy) is used as a kinetic and spectroscopic probe to investigate the Zn binding domains in the mouse 7S nerve growth factor protein (7S NGFn) and the Zn-insulin hexamer (In)6(Zn2+)2. The stopped-flow rapid-mixing kinetic time courses for the sequestering and removal of Zn2+ from both of these Zn metalloprotein hormones are remarkably biphasic. The fast phase of each reaction is 2nd order overall: 1st order in Terpy and 1st order in protein-bound Zn2+. Although the spectral changes associated with the slow phase correspond to the uptake of 1 mol of Terpy per g-atom of Zn2+, the slow phase is a 1st-order process (zero order in Terpy). The concentration dependencies and spectral changes are consistent with a common reaction mechanism for both proteins; the fast phase involves the formation of a mono(Terpy)-Zn(II)-protein complex at each Zn site, and the slow phase involves the rate-limiting dissociation of the Terpy-bound Zn2+ from the protein, followed by the rapid coordination of a 2nd Terpy molecule and formation of the bis(Terpy)-Zn(II) complex. In contrast, the reactions of Terpy with carboxypeptidases A and B, carbonic anhydrase, thermolysin and horse liver alcohol dehydrogenase all were very slow (t1/2 [half-life] of hours to days). In each case, the time course was described by a single exponential. The high-resolution X-ray structure of (In)6(Zn2+)2 provides a satisfying structural rationale for the biphasic time course. Each of the 2 Zn2+ is hexacoordinate. Three of the ligands are water molecules; the remaining 3 are imidazolyl moieties of His-B10. Based on this structural information, the rapid phase of the reaction involves displacement of the 3 water molecules by the tridentate Terpy. The striking similarities between the reactions of 7S NGFn and (In)6(Zn2+)2 with Terpy suggest the existence of structural similarity in the Zn binding domains of 7S NGFn and (In)6(Zn2+)2.