Single-molecule studies of group II intron ribozymes
Single-molecule studies of group II intron ribozymes
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DOI：
10.1073/pnas.0804034105
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发表时间：
2008-09-16
影响因子：
11.1
通讯作者：
Rueda, David
中科院分区：
文献类型：
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作者：
Steiner, Miriam;Karunatilaka, Krishanthi S.;Rueda, David
第二组内含子核酶通过一个独特的逐步过程折叠成其天然结构，该过程包括最初的缓慢压实，然后以依赖于镁的方式快速形成天然状态。单分子荧光显示了动态平衡中的三种不同的路径构象，它们由相对较小的激活势垒连接起来。从最稳定的近自然状态，达到未观察到的催化活性构象。这种最紧密的构象只在20 mM的镁离子以上短暂出现，并由底物结合稳定，这共同解释了核酶缓慢切割的原因。结构动力学随着镁离子浓度的增加而增加，使酶达到其活性状态。
Group II intron ribozymes fold into their native structure by a unique stepwise process that involves an initial slow compaction followed by fast formation of the native state in a Mg2+-dependent manner. Single-molecule fluorescence reveals three distinct on-pathway conformations in dynamic equilibrium connected by relatively small activation barriers. From a most stable near-native state, the unobserved catalytically active conformer is reached. This most compact conformer occurs only transiently above 20 mM Mg2+ and is stabilized by substrate binding, which together explain the slow cleavage of the ribozyme. Structural dynamics increase with increasing Mg2+ concentrations, enabling the enzyme to reach its active state.