Editing by a tRNA Synthetase: DNA Aptamer-Induced Translocation and Hydrolysis of a Misactivated Amino Acid

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• 作者：Mark A. Farrow and Paul Schimmel
• 刊名：Biochemistry
• 出版年：2001
• 出版时间：April 10, 2001
• 年：2001
• 卷：40
• 期：14
• 页码：4478 - 4483
• 全文大小：70K
• 年卷期：v.40,no.14(April 10, 2001)
• ISSN：1520-4995

文摘

Aminoacyl-tRNA synthetases establish the rules of the genetic code by aminoacylation reactions.Occasional activation of the wrong amino acid can lead to errors of protein synthesis. For isoleucyl-tRNA synthetase, these errors are reduced by tRNA-dependent hydrolytic editing reactions that occur ata site 25 Å from the active site. These reactions require that the misactivated amino acid be translocatedfrom the active site to the center for editing. One mechanism describes translocation as requiring themischarging of tRNA followed by a conformational change in the tRNA that moves the amino acid fromone site to the other. Here a specific DNA aptamer is investigated. The aptamer can stimulate aminoacid-specific editing but cannot be aminoacylated. Although the aptamer could in principle stimulatehydrolysis of a misactivated amino acid by an idiosyncratic mechanism, the aptamer is shown here toinduce translocation and hydrolysis of misactivated aminoacyl adenylate at the same site as that seenwith the tRNA cofactor. Thus, translocation to the site for editing does not require joining of the aminoacid to the nucleic acid. Further experiments demonstrated that aptamer-induced editing is sensitive toaptamer sequence and that the aptamer is directed to a site other than the active site or tRNA binding siteof the enzyme.