A conformational change in the ribosomal peptidyl transferase center upon active/inactive transition
A conformational change in the ribosomal peptidyl transferase center upon active/inactive transition
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DOI：
10.1073/pnas.171319598
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发表时间：
2001-08-28
影响因子：
11.1
通讯作者：
Barta, A
中科院分区：
文献类型：
--
作者：
Bayfield, MA;Dahlberg, AE;Barta, A
核糖体是一种动态粒子，在翻译过程中会发生许多结构变化。我们通过硫酸二甲酯（DMS）的化学探测表明，构象变化发生在几个核苷酸的肽基转移酶中心的pH值，温度和单价离子浓度的变化后，与埃尔森和同事超过30年前所作的观察一致。此外，我们已经发现，在23 S rRNA肽基转移酶区域的中心的A2451的pH依赖性DMS反应性，归因于该基地的扰动pKa，只发生在无活性的50 S和70 S核糖体。无活性核糖体中该碱基的DMS反应性程度取决于单价离子的身份和数量。此外，G2447，一个残基提出是关键的假设pKa扰动，是不是必要的条件DMS反应性在A2451。鉴于在A2451的DMS反应性的pH依赖性变化只发生在无活性的核糖体中，并且这种DMS反应性可以随着盐的增加而增加（与pH无关），我们得出结论，这一观察结果不能用作最近提出的酸/碱催化的核糖体转肽模型的支持证据。
sThe ribosome is a dynamic particle that undergoes many structural changes during translation. We show through chemical probing with dimethyl sulfate (DMS) that conformational changes occur at several nucleotides in the peptidyl transferase center upon alterations in pH, temperature, and monovalent ion concentration, consistent with observations made by Elson and coworkers over 30 years ago. Moreover, we have found that the pH-dependent DMS reactivity of A2451 in the center of the 23S rRNA peptidyl transferase region, ascribed to a perturbed pKa of this base, occurs only in inactive 50S and 70S ribosomes. The degree of DMS reactivity of this base in the inactive ribosomes depends on both the identity and amount of monovalent ion present. Furthermore, G2447, a residue proposed to be critical for the hypothesized pKa perturbation, is not essential for the conditional DMS reactivity at A2451. Given that the pH-dependent change in DMS reactivity at A2451 occurs only in inactive ribosomes, and that this DMS reactivity can increase with increasing salt (independently of pH), we conclude that this observation cannot be used as supporting evidence for a recently proposed model of acid/base catalyzed ribosomal transpeptidation.