Otvos J D, Engeseth H R, Nettesheim D G, Hilt C R
Department of Chemistry, University of Wisconsin-Milwaukee 53201.
Experientia Suppl. 1987;52:171-8. doi: 10.1007/978-3-0348-6784-9_10.
Different methods of preparing rabbit liver 113Cd,ZnMT in vitro were investigated in an attempt to reproduce the distinctive and reproducible manner in which the metals are distributed between the 2 clusters in vivo in protein produced in response to Cd administration. 113Cd NMR was used to demonstrate that the native metal distribution is not produced by Cd displacement of Zn from ZnMT, but rather by a direct metal interchange reaction between CdMT and ZnMT. Kinetic studies of this heretofore unknown reaction indicate that even at low physiological concentrations, CdMT and ZnMT cannot coexist without rapidly exchanging metals to produce mixed-metal protein species containing Cd and Zn located preferentially in the 4- and 3-metal clusters, respectively. The self-exchange reaction of Cd among the 7 binding sites of CdMT was also investigated and it was found that exchange of Cd among sites in the 3-metal cluster was very rapid (time-scale of seconds) while among sites of the 4-metal cluster or between clusters it was several orders of magnitude slower.
研究了多种体外制备兔肝113Cd,ZnMT的方法，试图重现体内金属在响应镉给药而产生的蛋白质中两个簇之间独特且可重复的分布方式。利用113Cd NMR证明，天然金属分布不是由镉从ZnMT中置换锌产生的，而是由CdMT和ZnMT之间的直接金属交换反应产生的。对这种前所未知反应的动力学研究表明，即使在低生理浓度下，CdMT和ZnMT也不能共存，而是会迅速交换金属，以产生分别优先位于4金属簇和3金属簇中的含镉和锌的混合金属蛋白物种。还研究了Cd在CdMT的7个结合位点之间的自交换反应，发现Cd在3金属簇位点之间的交换非常迅速（时间尺度为秒），而在4金属簇位点之间或簇之间的交换则慢几个数量级。
