Bassi G S, Murchie A I, Walter F, Clegg R M, Lilley D M
CRC Nucleic Acid Structure Research Group, Department of Biochemistry, The University, Dundee DD1 4HN, UK.
EMBO J. 1997 Dec 15;16(24):7481-9. doi: 10.1093/emboj/16.24.7481.
The ion-induced folding transitions of the hammerhead ribozyme have been analysed by fluorescence resonance energy transfer. The hammerhead ribozyme may be regarded as a special example of a three-way RNA junction, the global structure of which has been studied by comparing the distances (as energy transfer efficiencies) between the ends of pairs of labelled arms for the three possible end-to-end vectors as a function of magnesium ion concentration. The data support two sequential ion-dependent transitions, which can be interpreted in the light of the crystal structures of the hammerhead ribozyme. The first transition corresponds to the formation of a coaxial stacking between helices II and III; the data can be fully explained by a model in which the transition is induced by a single magnesium ion which binds with an apparent association constant of 8000-10 000 M-1. The second structural transition corresponds to the formation of the catalytic domain of the ribozyme, induced by a single magnesium ion with an apparent association constant of approximately 1100 M-1. The hammerhead ribozyme provides a well-defined example of ion-dependent folding in RNA.
通过荧光共振能量转移分析了锤头状核酶的离子诱导折叠转变。锤头状核酶可被视为三向RNA连接体的一个特殊例子，其整体结构已通过比较三种可能的端对端向量的标记臂对末端之间的距离（作为能量转移效率）随镁离子浓度的变化进行了研究。数据支持两个连续的离子依赖性转变，这可以根据锤头状核酶的晶体结构来解释。第一个转变对应于螺旋II和III之间形成同轴堆积；该转变由单个镁离子诱导，其表观缔合常数为8000 - 10000 M⁻¹，这一模型能够充分解释相关数据。第二个结构转变对应于核酶催化结构域的形成，由单个镁离子诱导，其表观缔合常数约为1100 M⁻¹。锤头状核酶为RNA中离子依赖性折叠提供了一个明确的例子。
