Zinc transfer potentials of the alpha - and beta-clusters of metallothionein are affected by domain interactions in the whole molecule.
Zinc transfer potentials of the alpha - and beta-clusters of metallothionein are affected by domain interactions in the whole molecule.
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DOI：
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发表时间：
2000
影响因子：
11.1
通讯作者：
L. Jiang;M. Vašák;B. Vallée;W. Maret
中科院分区：
文献类型：
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作者：
L. Jiang;M. Vašák;B. Vallée;W. Maret
通过化学合成获得的人金属硫蛋白（异构体 2）的 α 和 β 多肽被转化为其各自的锌/硫醇盐簇，并且分别研究每个结构域。 N 端 β 结构域的质子滴定数据符合一个简单模型，该模型具有相同表观 pK(a) 值 4.9 的三个电离以及在 pH 7.0 下锌的集体结合常数 5 x 10(-12) M。 C 端 α 结构域中的锌簇比 β 结构域中的锌簇更稳定。其 pH 滴定也更加复杂，表明至少有两类具有不同亲和力的锌位点。整个分子的各个结构域都是稳定的。化学修饰意味着赖氨酸侧链参与β结构域簇的稳定和整个分子中结构域的相互稳定。这两个锌簇的半胱氨酸硫的反应性以及根据其类型和特性向受体分子提供锌的潜力也有所不同。与分离的 α 结构域簇相比，分离的 β 结构域簇与埃尔曼试剂的反应更快，并且是针对贫锌山梨醇脱氢酶的更好的锌供体，而当螯合剂是锌受体时观察到相反的情况。因此，尽管每个簇彼此独立地组装，但各个结构域的累积特性不足以在结构或功能上描述金属硫蛋白。整个分子的两域结构对于其与配体的相互作用以及对其反应性和整体构象的控制非常重要。
The alpha- and beta-polypeptides of human metallothionein (isoform 2), obtained by chemical synthesis, were converted into their respective zinc/thiolate clusters, and each domain was investigated separately. Proton titration data for the N-terminal beta-domain fit a simple model with three ionizations of the same apparent pK(a) value of 4.9 and a collective binding constant for zinc of 5 x 10(-12) M at pH 7.0. The zinc cluster in the C-terminal alpha-domain is more stable than that in the beta-domain. Its pH titration is also more complex, indicating at least two classes of zinc sites with different affinities. The whole molecule is stabilized with regard to the individual domains. Chemical modification implicates lysine side chains in both the stabilization of the beta-domain cluster and the mutual stabilization of the domains in the whole molecule. The two zinc clusters also differ in the reactivity of their cysteine sulfurs and their potential to donate zinc to an acceptor molecule dependent on its type and characteristics. The isolated beta-domain cluster reacts faster with Ellman's reagent and is a better zinc donor toward zinc-depleted sorbitol dehydrogenase than is the isolated alpha-domain cluster, whereas the reverse is observed when a chelating agent is the zinc acceptor. Thus, although each cluster assembles independently of the other, the cumulative properties of the individual domains do not suffice to describe metallothionein either structurally or functionally. The two-domain structure of the whole molecule is important for its interaction with ligands and for control of its reactivity and overall conformation.