Structural Basis for the Exceptional Stability of Bisaminoacylated Nucleotides and Transfer RNAs

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• 作者：Maria Duca ; Carl O. Trindle ; Sidney M. Hecht
• 刊名：Journal of the American Chemical Society
• 出版年：2011
• 出版时间：July 27, 2011
• 年：2011
• 卷：133
• 期：29
• 页码：11368-11377
• 全文大小：1078K
• 年卷期：v.133,no.29(July 27, 2011)
• ISSN：1520-5126

文摘

At least one bisaminoacyl-tRNA is synthesized in nature (by Thermus thermophilus phenylalanyl-tRNA synthetase), and many disubstituted tRNAs have been prepared in vitro. Such misacylated tRNAs are able to participate in protein synthesis, even though they lack the free 2鈥?OH group of the 3鈥?terminal adenosine moiety. Their ready participation in protein synthesis implies significant chemical reactivity. The basis for this reactivity has been documented previously. Surprisingly, the aminoacyl moieties of these tRNAs also exhibit exceptional chemical stability. In the present report, bisaminoacylated nucleotides are investigated computationally and experimentally to define the basis for the stability of such species. Molecular modeling of bisalanyl-AMP in the absence of solvent and in the presence of a limited number of water molecules revealed two common features among the low-energy structures. The first was the presence of H-bonding interactions between the two aminoacyl moieties. The second was the presence of a H-bonding interaction between the 2鈥?O-alanyl moiety and the N-3 atom of the adenine nucleobase, typically mediated through a water molecule. The prediction of an interaction between an aminoacyl moiety and the adenine nucleobase was confirmed experimentally by comparing the behavior of bisalanyl-AMP and bisalanyl-UMP in the presence of model nucleophiles. This study suggests a possible role for the adenosine moiety at the 3鈥?end of aminoanyl-tRNAs in controlling the stability and reactivity of the aminoacyl moiety and has important implications for the reactivity and stability of normal aminoacyl-tRNAs.