MODEL FOR MAMMALIAN METALLOTHIONEIN STRUCTURE
MODEL FOR MAMMALIAN METALLOTHIONEIN STRUCTURE
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DOI：
10.1073/pnas.80.6.1501
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发表时间：
1983-01-01
期刊：
影响因子：
--
通讯作者：
ARMITAGE, IM
中科院分区：
文献类型：
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作者：
BOULANGER, Y;GOODMAN, CM;ARMITAGE, IM
哺乳动物金属硫蛋白的理化研究结果进行了总结，并提出了一个模型的蛋白质。所有哺乳动物金属硫蛋白的一级结构是非常同源的，有38个不变的残基，其中20个是半胱氨酸。UV和CD [圆二色性]光学研究的结果表明，所有20个半胱氨酸都参与7摩尔金属/摩尔金属硫蛋白的连接，并且该蛋白质不含任何α-半胱氨酸。螺旋结构通过Chou-Fasman方法的理论分析预测了11 β-弯曲，每一个涉及至少1个半胱氨酸残基。最重要的结构数据，由113镉NMR，表明7摩尔的结合镉2+被安排在2个单独的金属簇，一个含有4个金属离子，另一个含有3个，与所有的镉2+四面体配位半胱氨酸硫醇配体。金属硫蛋白链的羧基末端部分的11个半胱氨酸残基（残基30-61）连接到4-金属簇，如该酶裂解片段的113 Cd NMR所示。来自氨基末端多肽部分的剩余半胱氨酸残基（残基1-29）形成3-金属簇。这种链的分裂与小鼠金属硫蛋白-1基因中对应于多肽链中残基32的内含子的存在一致。一个2域的分子模型构建的基础上分析所有可用的数据，并详细描述。该模型的准确性通过1H NMR在500 MHz进行了测试，数据与建议的结构一致。
The results of physicochemical studies of mammalian metallothioneins are summarized and used to propose a model of the protein. The primary structures of all mammalian metallothioneins are very homologous; there are 38 invariant residues and 20 of them are cysteines. The results of UV and CD [circular dichroism] optical studies indicated that all 20 cysteines are involved in the ligation of 7 mol of metal/mol of metallothionein and that the protein does not contain any .alpha.-helix structure. A theoretical analysis by the Chou-Fasman method has predicted 11 .beta.-bends, each one involving at least 1 cysteine residue. The most significant structural data, provided by 113Cd NMR, demonstrated that the 7 mol of bound Cd2+ are arranged in 2 separate metal clusters, one containing 4 metal ions and the other containing 3, with all Cd2+ tetrahedrally coordinated to cysteine thiolate ligands. The 11 cysteine residues of the carboxyl-terminal portion of the metallothionein chain (residues 30-61) are ligated to the 4-metal cluster as shown by 113Cd NMR of this enzymatically cleaved fragment. The remaining cysteine residues from the amino-terminal polypeptide portion (residues 1-29) form the 3-metal cluster. Such a division of the chain is consistent with the presence of an intron in the mouse metallothionein-1 gene corresponding to residue 32 in the polypeptide chain. A 2-domain molecular model was constructed based on an analysis of all the available data and is described in detail. The accuracy of this model was tested by 1H NMR at 500 MHz and the data are in agreement with the proposed structure.