Identity Elements for Specific Aminoacylation of a tRNA by Mammalian Lysyl-tRNA Synthetase Bearing a Nonspecific tRNA-Interacting Factor

详细信息    查看全文

• 作者：Mathilde Francin ; Marc Mirande
• 刊名：Biochemistry
• 出版年：2006
• 出版时间：August 22, 2006
• 年：2006
• 卷：45
• 期：33
• 页码：10153 - 10160
• 全文大小：263K
• 年卷期：v.45,no.33(August 22, 2006)
• ISSN：1520-4995

文摘

Mammalian lysyl-tRNA synthetase (LysRS) has an N-terminal polypeptide chain extensionappended to a prokaryotic-like synthetase domain. This extension, termed a tRNA-interacting factor (tIF),possesses a RNA-binding motif [KxxxK(K/R)xxK] that binds nonspecifically the acceptor TC stem-loop domain of tRNA and provides a potent tRNA binding capacity to this enzyme. Consequently, nativeLysRS aminoacylates a RNA minihelix mimicking the amino acid acceptor stem-loop domain of tRNA₃^Lys.Here, examination of minihelix recognition showed that mammalian LysRS aminoacylates RNA miniheliceswithout specificity of sequence, revealing that none of the nucleotides from the acceptor TC stem-loop domain are essential determinants of tRNA^Lys acceptor identity. To test whether the tIF domainreduces the specificity of the synthetase with regard to complete tRNA molecules, aminoacylation ofwild-type and mutant noncognate tRNAs by wild-type or N-terminally truncated LysRS was examined.The presence of the UUU anticodon of tRNA^Lys appeared to be necessary and sufficient to transformyeast tRNA^Asp or tRNA_i^Met into potent lysine acceptor tRNAs. Thus, nonspecific RNA-protein interactionsbetween the acceptor stem of tRNA and the tIF domain do not relax the tRNA specificity of mammalianLysRS. The possibility that interaction of the full-length cognate tRNA with the synthetase is required toinduce the catalytic center of the enzyme into a productive conformation is discussed.