Ribosomal features essential for tna operon induction:: Tryptophan binding at the peptidyl transferase center
Ribosomal features essential for tna operon induction:: Tryptophan binding at the peptidyl transferase center
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DOI：
10.1128/jb.01869-06
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发表时间：
2007-04-01
影响因子：
3.2
通讯作者：
Yanofsky, Charles
中科院分区：
文献类型：
--
作者：
Cruz-Vera, Luis R.;New, Aaron;Yanofsky, Charles
TnaC新生肽的氨基酸序列的特征被翻译核糖体识别。识别导致翻译核糖体内的色氨酸结合，抑制tnaC翻译的终止并防止tna操纵子前导区中的Rho依赖性转录终止。先前表明，在751位插入腺嘌呤残基或在23 S rRNA中引入U2609 C改变或在核糖体蛋白L22中引入K90 W替换阻止色氨酸诱导tna操纵子表达。还观察到23 S rRNA的752位的腺嘌呤是诱导所必需的。在目前的研究中，对这些改变的核糖体缺乏诱导的解释进行了研究。使用分离的TnaC-核糖体复合物，结果表明，虽然色氨酸抑制嘌呤霉素切割TnaC-tRNA（Pro）与野生型核糖体复合物，它不抑制切割与四个突变体核糖体复合物检查。类似地，色氨酸阻止了稀疏霉素对野生型核糖体复合物的TnaC-tRNA（Pro）切割的抑制，但对这些突变体核糖体复合物没有。此外，位于肽基转移酶中心附近的核苷酸A2572，其被野生型核糖体复合物保护免于色氨酸甲基化，但未被突变型核糖体复合物保护。这些发现鉴定了位于核糖体出口通道中的识别TnaC肽特征的特定核糖体残基。这种识别在肽基转移酶中心产生游离色氨酸结合位点，其中结合的色氨酸抑制肽基转移酶活性。
Features of the amino acid sequence of the TnaC nascent peptide are recognized by the translating ribosome. Recognition leads to tryptophan binding within the translating ribosome, inhibiting the termination of tnaC translation and preventing Rho-dependent transcription termination in the tna operon leader region. It was previously shown that inserting an adenine residue at position 751 or introducing the U2609C change in 23S rRNA or introducing the K90W replacement in ribosomal protein L22 prevented tryptophan induction of tna operon expression. It was also observed that an adenine at position 752 of 23S rRNA was required for induction. In the current study, the explanation for the lack of induction by these altered ribosomes was investigated. Using isolated TnaC-ribosome complexes, it was shown that although tryptophan inhibits puromycin cleavage of TnaC-tRNA(Pro) with wild-type ribosome complexes, it does not inhibit cleavage with the four mutant ribosome complexes examined. Similarly, tryptophan prevents sparsomycin inhibition of TnaC-tRNA(Pro) cleavage with wild-type ribosome complexes but not with these mutant ribosome complexes. Additionally, a nucleotide located close to the peptidyl transferase center, A2572, which was protected from methylation by tryptophan with wild-type ribosome complexes, was not protected with mutant ribosome complexes. These findings identify specific ribosomal residues located in the ribosome exit tunnel that recognize features of the TnaC peptide. This recognition creates a free tryptophan-binding site in the peptidyl transferase center, where bound tryptophan inhibits peptidyl transferase activity.