An uncharged amine in the transition state of the ribosornal peptidyl transfer reaction
An uncharged amine in the transition state of the ribosornal peptidyl transfer reaction
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DOI：
10.1016/j.chembiol.2008.04.005
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发表时间：
2008-05-01
影响因子：
--
通讯作者：
Strobel, Scott A.
中科院分区：
文献类型：
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作者：
Kingery, David A.;Pfund, Emmanuel;Strobel, Scott A.
核糖体有一个由催化肽键形成的RNA组成的活性位点。要了解RNA如何促进这种反应，需要对化学过渡态有详细的了解。本文报道了a-氨基亲核试剂与一系列嘌呤霉素衍生物的Bronsted系数。在化学限速条件下，50S亚基和70S核糖体催化的反应均表现出线性自由能关系，斜率接近于零。这些结果表明，在过渡状态下，亲核试剂在核糖体催化的反应中是中性的，而在典型的非催化的氨解反应中则带有大量的正电荷。这表明核糖体过渡态涉及到与氮碳键形成相当程度的去质子化。这种过渡态与溶液中未催化的氨解反应有明显不同。
The ribosome has an active site comprised of RNA that catalyzes peptide bond formation. To understand how RNA promotes this reaction requires a detailed understanding of the chemical transition state. Here, we report the Bronsted coefficient of the a-amino nucleophile with a series of puromycin derivatives. Both 50S subunit- and 70S ribosome-catalyzed reactions displayed linear free-energy relationships with slopes close to zero under conditions where chemistry is rate limiting. These results indicate that, at the transition state, the nucleophile is neutral in the ribosome-catalyzed reaction, in contrast to the substantial positive charge reported for typical uncatalyzed aminolysis reactions. This suggests that the ribosomal transition state involves deprotonation to a degree commensurate with nitrogen-carbon bond formation. Such a transition state is significantly different from that of uncatalyzed aminolysis reactions in solution.