Structure of mammalian metallothionein.
Structure of mammalian metallothionein.
复制标题
哺乳动物金属硫蛋白的结构。
DOI：
10.1289/ehp.845493
复制
发表时间：
1984
影响因子：
10.4
通讯作者：
M. Good
中科院分区：
文献类型：
--
作者：
J. Kägi;M. Vašák;K. Lerch;D. Gilg;P. Hunziker;W. R. Bernhard;M. Good
所有的哺乳动物金属硫蛋白都包含一个由61个氨基酸残基组成的单肽链，其中20个半胱氨酸为7个金属结合位点提供配体。天然金属硫蛋白在金属组成上通常是不均匀的，锌、镉和铜以不同的比例出现。然而，现在已经通过体外重组从无金属载子蛋白制备了仅含有单一金属的形式，即Zn， Cd, Ni, Co, Hg, Pb, Bi。通过对这些衍生物的光谱分析，确定了所有半胱氨酸残基都参与金属结合，每个金属离子都与四个硫酸盐配体结合，并且每个配合物的对称性接近于四面体。为了满足Me7(Cys-)20整体化学计量的要求，配合物必须结合形成金属-硫代盐簇结构。这种星团存在的实验证据来自光谱和磁性手段对金属-金属相互作用的证明。因此，在Co(II)7-金属硫蛋白中，Co（II）特异性ESR信号被并列顺磁性金属离子的反铁磁耦合有效抑制。通过监测Co（II）逐步掺入蛋白质时发生的ESR信号大小的变化，可以跟踪簇的形成。这个过程是两个阶段的。直到四等价物Co（II）结合时，ESR振幅随金属含量的增加而增加，表明产生了磁性非相互作用的高自旋配合物。然而，当加入其余三种Co（II）时，这些特征逐渐被抑制，这表明团簇的形成。Cd和Hg的簇形成模式也有相同的记录。簇和多肽链的实际空间组织仍有待确定。一个有吸引力的可能性是四面体金属硫酸盐在金刚烷状结构中被提供配体的适当折叠的链段包围。1H-NMR数据和红外吸收测量结果与富含β型构象的紧密折叠结构一致。
All mammalian metallothioneins characterized contain a single polypeptide chain of 61 amino acid residues, among them 20 cysteines providing the ligands for seven metal-binding sites. Native metallothioneins are usually heterogeneous in metal composition, with Zn, Cd, and Cu occurring in varying proportions. However, forms containing only a single metal species, i.e., Zn, Cd, Ni, Co, Hg, Pb, Bi, have now been prepared by in vitro reconstitution from the metal-free apoprotein. By spectroscopic analysis of such derivatives it was established that all cysteine residues participate in metal binding, that each metal ion is bound to four thiolate ligands, and that the symmetry of each complex is close to that of a tetrahedron. To satisfy the requirements of the overall Me7(Cys-)20 stoichiometry, the complexes must be combined to form metal-thiolate cluster structures. Experimental proof for the occurrence of such clusters comes from the demonstration of metal-metal interactions by spectroscopic and magnetic means. Thus, in Co(II)7-metallothionein, the Co(II)-specific ESR signals are effectively suppressed by antiferromagnetic coupling of juxtaposed paramagnetic metal ions. By monitoring changes in ESR signal size occurring on stepwise incorporation of Co(II) into the protein, it is possible to follow the building up of the clusters. This process is biphasic. Up to binding of four equivalents of Co(II), the ESR amplitude increases in proportion to the metal content, indicating generation of magnetically noninteracting high-spin complexes. However, upon addition of the remaining three equivalents of Co(II), these features are progressively suppressed, signaling the formation of clusters. The same mode of cluster formation has also been documented for Cd and Hg. The actual spatial organization of the clusters and the polypeptide chain remains to be established. An attractive possibility is the arrangement of the tetrahedral metal-thiolates in adamantane-like structures surrounded by properly folded segments of the chain providing the ligands. 1H-NMR data and infrared absorption measurements are consistent with a tightly folded structure rich in beta-type conformation.
DOI：
10.1073/pnas.80.6.1501
发表时间：
1983-01-01
期刊：
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA-BIOLOGICAL SCIENCES
影响因子：
--
作者：
BOULANGER, Y;GOODMAN, CM;ARMITAGE, IM
通讯作者：
ARMITAGE, IM