Celander D W, Cech T R
Howard Hughes Medical Institute, Department of Chemistry and Biochemistry, University of Colorado, Boulder 80309-0215.
Science. 1991 Jan 25;251(4992):401-7. doi: 10.1126/science.1989074.
The higher order folding process of the catalytic RNA derived from the self-splicing intron of Tetrahymena thermophila was monitored with the use of Fe(II)-EDTA-induced free radical chemistry. The overall tertiary structure of the RNA molecule forms cooperatively with the uptake of at least three magnesium ions. Local folding transitions display different metal ion dependencies, suggesting that the RNA tertiary structure assembles through a specific folding intermediate before the catalytic core is formed. Enzymatic activity, assayed with an RNA substrate that is complementary to the catalytic RNA active site, coincides with the cooperative structural transition. The higher order RNA foldings produced by Mg(II), Ca(II), and Sr(II) are similar; however, only the Mg(II)-stabilized RNA is catalytically active. Thus, these results directly demonstrate that divalent metal ions participate in general folding of the ribozyme tertiary structure, and further indicate a more specific involvement of Mg(II) in catalysis.
利用Fe(II)-EDTA诱导的自由基化学方法监测了嗜热四膜虫自剪接内含子来源的催化RNA的高阶折叠过程。RNA分子的整体三级结构在摄取至少三个镁离子时协同形成。局部折叠转变表现出不同的金属离子依赖性，这表明RNA三级结构在催化核心形成之前通过特定的折叠中间体组装而成。用与催化RNA活性位点互补的RNA底物测定的酶活性与协同结构转变一致。由Mg(II)、Ca(II)和Sr(II)产生的高阶RNA折叠相似；然而，只有Mg(II)稳定的RNA具有催化活性。因此，这些结果直接证明二价金属离子参与核酶三级结构的一般折叠，并进一步表明Mg(II)在催化中具有更特殊的作用。
