Escherichia coli tRNA(4)(Arg)(UCU) induces a constrained conformation of the crucial Omega-loop of arginyl-tRNA synthetase

• Published in: Biochemical and biophysical research communications 2004-01, Vol.313 (1), p.129-134
• Main Authors: Yao, Yong-Neng, Zhang, Qing-Shuo, Yan, Xian-Zhong, Zhu, Guang, Wang, En-Duo
• Format: Article
• Language: English
• Subjects: Arginine - metabolism; Arginine-tRNA Ligase - chemistry; Arginine-tRNA Ligase - metabolism; Catalytic Domain; Escherichia coli - enzymology; Kinetics; Models, Molecular; Nuclear Magnetic Resonance, Biomolecular - methods; Protein Conformation; RNA, Transfer, Arg - genetics; RNA, Transfer, Arg - metabolism; Tryptophan - analogs & derivatives; Tryptophan - metabolism
• ISSN: 0006-291X
• DOI: 10.1016/j.bbrc.2003.11.107

Previous investigations show that tRNA(Arg)-induced conformational changes of arginyl-tRNA synthetase (ArgRS) Omega-loop region (Escherichia coli (E. coli), Ala451-Ala457) may contribute to the productive conformation of the enzyme catalytic core, and E. coli tRNA(2)(Arg)(ICG)-bound and -free conformations of the Omega-loop exchange at an intermediate rate on NMR timescale. Herein, we report that E. coli ArgRS catalyzes tRNA(2)(Arg)(ICG) and tRNA(4)(Arg)(UCU) with similar efficiencies. However, 19F NMR spectroscopy of 4-fluorotryptophan-labeled E. coli ArgRS reveals that the tRNA(4)(Arg)(UCU)-bound and -free conformations of the Omega-loop region interconvert very slowly and the lifetime of bound conformation is much longer than 0.33 ms. Therefore, tRNA(4)(Arg)(UCU) differs from tRNA(2)(Arg)(ICG) in the conformation-exchanging rate of the Omega-loop. Comparative structure model of E. coli ArgRS is presented to rationalize these 19F NMR data. Our 19F NMR and catalytic assay results suggest that the tRNA(Arg)-induced conformational changes of Omega-loop little contribute to the productive conformation of ArgRS catalytic core.