111Cd NMR studies of the domain specificity of Ag+ and Cu+ binding to metallothionein.
111Cd NMR studies of the domain specificity of Ag+ and Cu+ binding to metallothionein.
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DOI：
10.1021/bi961401n
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发表时间：
1996-11
期刊：
影响因子：
2.9
通讯作者：
H. Li;J. Otvos
中科院分区：
文献类型：
--
作者：
H. Li;J. Otvos
用~（111）Cd NMR研究了Cd_（7 MT）与Ag ~+、Cu ~+的金属置换反应以及Cd_（7 MT）与Ag_（12）MT、Cu_（12）MT的蛋白间金属交换反应。用Ag+滴定111 Cd 7 MT表明Ag+优先结合蛋白质的β结构域以形成金属杂合物物种（Cd 4）α（Ag 6）β MT。一旦β-结构域被填充，额外的Ag+离子从α-结构域置换Cd 2+以形成（Ag 6）α（Ag 6）β MT。金属置换反应是协同的，并且两个域彼此独立地反应。（Cd 4）alpha（Ag 6）beta MT杂合蛋白也作为Cd 7 MT和Ag 12 MT之间直接蛋白间金属交换的主要产物形成。Cu+以与Ag+类似的方式与Cd 7 MT反应，其中添加6当量的Cu+导致优先形成（Cd 4）α（Cu 6）β-MT，并且添加12当量的Cu+导致形成（Cu 6）α（Cu 6）β MT。然而，与Ag+不同，Cu+似乎产生可能含有混合金属簇的中间物种。Cu 12-MT和Cd 7 MT之间的蛋白质间金属交换导致Cd 2+净转移到α结构域，Cu+净转移到β结构域。这两个域对一价和二价金属离子的不同亲和力加上金属交换的简易途径的可用性可能是使MT能够在不同金属离子的代谢中同时起作用的特征。
Metal displacement reactions of Cd7MT with Ag+ or Cu+ and interprotein metal exchange reactions between Cd7MT and Ag12MT or Cu12MT were studied by 111Cd NMR. Titration of 111Cd7MT with Ag+ indicates that Ag+ binds preferentially to the beta-domain of the protein to form the metal hybrid species, (Cd4)alpha(Ag6)beta MT. Once the beta-domain is filled, additional Ag+ ions displace Cd2+ from the alpha-domain to form (Ag6)alpha(Ag6)beta MT. The metal displacement reaction is cooperative and the two domains react independently of one another. The (Cd4)alpha(Ag6)beta MT hybrid protein is also formed as the major product of direct interprotein metal exchange between Cd7MT and Ag12MT. Cu+ reacts with Cd7MT in a manner similar to Ag+, with addition of 6 equiv of Cu+ leading to preferential formation of (Cd4)alpha(Cu6)beta-MT, and 12 equiv of Cu+ to formation of (Cu6)alpha(Cu6)beta MT. However, unlike Ag+, Cu+ appears to produce intermediate species that may contain mixed-metal clusters. Interprotein metal exchange between Cu12-MT and Cd7MT leads to the net transfer of Cd2+ into the alpha-domain and Cu+ into the beta-domain. The differential affinities of the two domains for monovalent and divalent metal ions plus the availability of facile pathways for metal exchange may be features that enable MT to function simultaneously in the metabolism of different metal ions.