RNA核酸内切酶的研究进展

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tRNA在蛋白质合成过程中起着极其重要的作用。在所有的生物体内，tRNA首先以前体形式转录，然后必需经过一系列的加工后才能成为有功能的tRNA分子。tRNase Z、RNase P和tRNA剪接内切酶是参与tRNA前体加工的三种主要的核酸内切酶，分别参与tRNA前体3'末端、tRNA前体5'末端和内含子剪接的加工。这三种酶具有不同的结构特征，并且利用完全不同的催化机制水解磷酸二酯键。tRNase Z和RNaseP都是金属酶，活性中心分别需要Zn2＋和Mg2＋的参与；而tRNA剪接内切酶活性中心不需要金属离子，是一个由不同催化亚基上的关键氨基酸残基构成的组合式活性中心。
tRNA plays a crucial role in protein synthesis. In all organisms, tRNAs are synthesized as precursors. To be functional, pre-tRNAs must undergo a number of processing steps. tRNase Z，RNase P and tRNA splicing endonuclease are three major endonucleases that participate in pre-tRNA processing. These three endonucleases have distinct structural features and use completely different catalytic mechanisms to hydrolyze the phosphodiester bond. tRNase Z and RNase P are metalloenzymes and their active centers require Zn2＋and Mg2＋，respectively. The active center of tRNA splicing endonuclease does not require metal ions, and is a composite active center consisting of key residues from different catalytic subunits.