title: Escherichia coli tRNA(4)(Arg)(UCU) induces a constrained conformation of the crucial Omega-loop of arginyl-tRNA synthetase.
abstract: 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.
authors.affiliation: State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, The Chinese Academy of Sciences, 320 Yue Yang Road, Shanghai 200031, PR China.
authors.forename: Yong-Neng
authors.initials: YN
authors.lastname: Yao
authors.forename: Qing-Shuo
authors.initials: QS
authors.lastname: Zhang
authors.forename: Xian-Zhong
authors.initials: XZ
authors.lastname: Yan
authors.forename: Guang
authors.initials: G
authors.lastname: Zhu
authors.forename: En-Duo
authors.initials: ED
authors.lastname: Wang
mesh_terms: D001120:Arginine / Q000378:metabolism; D001126:Arginine-tRNA Ligase / Q000737:chemistry* / Q000378:metabolism*; D020134:Catalytic Domain; D004926:Escherichia coli / Q000201:enzymology*; D007700:Kinetics; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods; D011487:Protein Conformation; D012347:RNA, Transfer, Arg / Q000235:genetics / Q000378:metabolism*; D014364:Tryptophan / Q000031:analogs & derivatives / Q000378:metabolism
chemical_list: D012347:RNA, Transfer, Arg; D014364:Tryptophan; D001120:Arginine; D001126:Arginine-tRNA Ligase