The Novel Chemical Mechanism of the Twister Ribozyme
The Novel Chemical Mechanism of the Twister Ribozyme
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DOI：
10.1021/jacs.5b11791
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发表时间：
2016-05-18
影响因子：
15
通讯作者：
Liiley, David M. J.
中科院分区：
文献类型：
--
作者：
Wilson, Timothy J.;Liu, Yijin;Liiley, David M. J.
我们描述了扭转酶核酶催化作用的多因素起源。我们提供的证据表明，紧邻易断裂磷酸（A1）3'端的腺嘌呤作为一种普通的酸起作用。环氮原子的取代表明，非常不寻常的A1的N3是氧阴离子离去基团的质子供体。A1被容纳在一个特定的结合口袋中，使其pK（a）向中性方向升高，并将其N3与O5'并列质子化，并有助于产生亲核攻击所需的直线轨迹。A1起一般酸催化作用，而G33起一般碱作用。一个100倍的立体特异性硫代磷酸酯在易裂磷酸盐的效果是一致的过渡态的显着稳定的核酶，在G33和官能团取代表明，其环外N2直接与易裂磷酸盐相互作用。提出了一个模型的核酶活性位点，容纳这些催化策略。
We describe the multifactorial origins of catalysis by the twister ribozyme. We provide evidence that the adenine immediately 3' to the scissile phosphate (A1) acts as a general acid. Substitution of ring nitrogen atoms indicates that very unusually the N3 of A1 is the proton donor to the oxyanion leaving group. A1 is accommodated in a specific binding pocket that raises its pK(a) toward neutrality, juxtaposes its N3 with the O5' to be protonated, and helps create the in-line trajectory required for nucleophilic attack. A1 performs general acid catalysis while G33 acts as a general base. A 100-fold stereospecific phosphorothioate effect at the scissile phosphate is consistent with a significant stabilization of the transition state by the ribozyme, and functional group substitution at G33 indicates that its exocyclic N2 interacts directly with the scissile phosphate. A model of the ribozyme active site is proposed that accommodates these catalytic strategies.