Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, Taiyuan 030006, PR China.
Arch Biochem Biophys. 2011 May 15;509(2):170-6. doi: 10.1016/j.abb.2011.02.015. Epub 2011 Feb 23.
Metallothioneins MTT1 and MTT2 from Tetrahymena thermophila have been characterized. The MTT1 contains mainly characteristic Cys-Cys-Cys and Cys-Cys clusters, but MTT2 contains mainly Cys-X-Cys cluster. Cd(16)-MTT1 mainly consists of α-helix and β-turns, in contrast, Cd(11)-MTT2 mainly consists of random coils. Reaction of Cd(16)-MTT1 and Cd(11)-MTT2 with nitric oxide leads to intramolecular disulfide bond formation, respectively. Binding stabilities of Cd(2+), Hg(2+) and Zn(2+) to MTT1 are stronger than those to MTT2. Cu(2+) can not replace Cd(2+) from Cd(16)-MTT1 complex, but can replace Cd(2+) from Cd(11)-MTT2 complex. The analysis of qRT-PCR revealed MTT2 mRNA levels were 31-fold higher than those of MTT1 under basal conditions. These results further suggest MTT1 possibly play a role in the detoxification of heavy metal ions, and MTT2 may be involved in the homeostasis of copper ions.
嗜热四膜虫金属硫蛋白 MTT1 和 MTT2 的特性已被阐明。MTT1 主要含有特征性的 Cys-Cys-Cys 和 Cys-Cys 簇，但 MTT2 主要含有 Cys-X-Cys 簇。Cd(16)-MTT1 主要由α-螺旋和β-转角组成，而 Cd(11)-MTT2 主要由无规卷曲组成。与一氧化氮反应后，Cd(16)-MTT1 和 Cd(11)-MTT2 分别形成分子内二硫键。MTT1 与 Cd(2+)、Hg(2+)和 Zn(2+)的结合稳定性强于 MTT2。Cu(2+)不能从 Cd(16)-MTT1 配合物中取代 Cd(2+)，但可以从 Cd(11)-MTT2 配合物中取代 Cd(2+)。qRT-PCR 分析显示，在基础条件下，MTT2mRNA 的水平比 MTT1 高 31 倍。这些结果进一步表明，MTT1 可能在重金属离子解毒中发挥作用，而 MTT2 可能参与铜离子的动态平衡。
