Purine bases at position 37 of tRNA stabilize codon-anticodon interaction in the ribosomal A site by stacking and Mg2+-dependent interactions
Purine bases at position 37 of tRNA stabilize codon-anticodon interaction in the ribosomal A site by stacking and Mg2+-dependent interactions
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DOI：
10.1261/rna.5142404
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发表时间：
2004-01-01
期刊：
影响因子：
4.5
通讯作者：
Katunin, VI
中科院分区：
文献类型：
--
作者：
Konevega, AL;Soboleva, NG;Katunin, VI
tRNA的反密码子环含有许多保守或不保守的核苷酸。在大多数tRNA中，在紧邻反密码子3'的37位发现高度修饰的嘌呤。在这里，我们研究的作用，在位置37 tRNA（苯丙氨酸）结合到大肠杆菌核糖体的A位点的碱基。测量天然酵母肽基-tRNA（Phe）与高度修饰的G（wybutine）或未修饰的肽基-tRNA（Phe）、在位置37处具有G、A、C或U的转录物的A位点结合的亲和力和速率常数。数据表明，嘌呤稳定结合，由于更强的堆叠和额外的相互作用与核糖体介导的Mg 2+离子。巴龙霉素是一种在解码中心与16 S rRNA结合的抗生素，它极大地稳定了A位点的tRNA，并消除了结合的Mg 2+依赖性。结合熵和熵的比较表明，在位置37处的碱基的超修饰不影响密码子-反密码子复合物中的堆叠，而是降低A位点结合的熵罚。在37位用嘧啶取代嘌呤增加了tRNA与A位点结合和解离的速率。这些数据表明，tRNA的A位点的初始结合之后，反密码子环或核糖体解码中心的限速重排，这是由嘌呤在位置37的青睐，并涉及更强的堆叠，额外的Mg 2+结合，并与16 S rRNA的相互作用。
The anticodon loop of tRNA contains a number of conserved or semiconserved nucleotides. In most tRNAs, a highly modified purine is found at position 37 immediately 3' to the anticodon. Here, we examined the role of the base at position 37 for tRNA(Phe) binding to the A site of Escherichia coli ribosomes. Affinities and rate constants of A-site binding of native yeast peptidyi-tRNA(Phe), with hypermodified G (wybutine), or of unmodified peptidyi-tRNA(Phe), transcripts with G, A, C, or U, at position 37 were measured. The data indicate that purines stabilize binding due to stronger stacking and additional interactions with the ribosome mediated by Mg2+ ions. Paromomycin, an antibiotic that binds to 16S rRNA in the decoding center, greatly stabilized tRNAs in the A site and abolished the Mg2+-dependence of binding. Comparison of binding enthalpies and entropies suggests that hypermodification of the base at position 37 does not affect stacking in the codon-anticodon complex, but rather decreases the entropic penalty for A-site binding. Substitution of purines with pyrimidines at position 37 increases the rates of tRNA binding to and dissociation from the A site. The data suggest that initial binding of tRNA to the A site is followed by a rate-limiting rearrangement of the anticodon loop or the ribosome decoding center that is favored by purines at position 37 and involves stronger stacking, additional Mg2+ binding, and interactions with 16S rRNA.