Crucial elements that maintain the interactions between the regulatory TnaC peptide and the ribosome exit tunnel responsible for Trp inhibition of ribosome function
Crucial elements that maintain the interactions between the regulatory TnaC peptide and the ribosome exit tunnel responsible for Trp inhibition of ribosome function
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DOI：
10.1093/nar/gkr1052
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发表时间：
2012-03-01
影响因子：
14.9
通讯作者：
Cruz-Vera, Luis R.
中科院分区：
文献类型：
--
作者：
Martinez, Allyson K.;Shirole, Nitin H.;Cruz-Vera, Luis R.
TnaC 新生肽的翻译在 L-色氨酸存在的情况下抑制核糖体活性，诱导大肠杆菌中 tnaCAB 操纵子的表达。这项工作利用化学甲基化揭示了 TnaC 和核糖体之间的相互作用如何受到两个分子突变的影响。核糖体内 TnaC-tRNA(Pro) 肽基-tRNA 的存在可保护 23S rRNA 核苷酸 U2609 免受化学甲基化。在含有 A748-A752 区域 23S rRNA 核苷酸变化的突变核糖体中没有观察到这种保护。核苷酸 A752 和 U2609 建立碱基对相互作用。大多数 A752 或 U2609 的替代品都会影响 TnaC 调节的 LacZ 报告基因的 Trp 诱导。然而，单一更换 A752G，或双重更换 A752G 和 U2609C，维持色氨酸诱导。保守 TnaC 残基 W12 和 D16 的替换也消除了 TnaC-tRNA(Pro) 对 U2609 的化学甲基化保护。这些数据表明，当核糖体对色氨酸有反应时，核糖体出口通道中的 TnaC 新生肽与 U2609 核苷酸相互作用。这种相互作用受到 23S rRNA 出口隧道核苷酸以及保守 TnaC 残基突变变化的影响，表明它们影响出口隧道的结构和/或隧道中的新生肽构型。
Translation of the TnaC nascent peptide inhibits ribosomal activity in the presence of l-tryptophan, inducing expression of the tnaCAB operon in Escherichia coli. Using chemical methylation, this work reveals how interactions between TnaC and the ribosome are affected by mutations in both molecules. The presence of the TnaC-tRNA(Pro) peptidyl-tRNA within the ribosome protects the 23S rRNA nucleotide U2609 against chemical methylation. Such protection was not observed in mutant ribosomes containing changes in 23S rRNA nucleotides of the A748-A752 region. Nucleotides A752 and U2609 establish a base-pair interaction. Most replacements of either A752 or U2609 affected Trp induction of a TnaC-regulated LacZ reporter. However, the single change A752G, or the dual replacements A752G and U2609C, maintained Trp induction. Replacements at the conserved TnaC residues W12 and D16 also abolished the protection of U2609 by TnaC-tRNA(Pro) against chemical methylation. These data indicate that the TnaC nascent peptide in the ribosome exit tunnel interacts with the U2609 nucleotide when the ribosome is Trp responsive. This interaction is affected by mutational changes in exit tunnel nucleotides of 23S rRNA, as well as in conserved TnaC residues, suggesting that they affect the structure of the exit tunnel and/or the nascent peptide configuration in the tunnel.