title: Human tryptophanyl-tRNA synthetase is switched to a tRNA-dependent mode for tryptophan activation by mutations at V85 and I311.
abstract: For most aminoacyl-tRNA synthetases (aaRS), their cognate tRNA is not obligatory to catalyze amino acid activation, with the exception of four class I (aaRS): arginyl-tRNA synthetase, glutamyl-tRNA synthetase, glutaminyl-tRNA synthetase and class I lysyl-tRNA synthetase. Furthermore, for arginyl-, glutamyl- and glutaminyl-tRNA synthetase, the integrated 3' end of the tRNA is necessary to activate the ATP-PPi exchange reaction. Tryptophanyl-tRNA synthetase is a class I aaRS that catalyzes tryptophan activation in the absence of its cognate tRNA. Here we describe mutations located at the appended beta1-beta2 hairpin and the AIDQ sequence of human tryptophanyl-tRNA synthetase that switch this enzyme to a tRNA-dependent mode in the tryptophan activation step. For some mutant enzymes, ATP-PPi exchange activity was completely lacking in the absence of tRNA(Trp), which could be partially rescued by adding tRNA(Trp), even if it had been oxidized by sodium periodate. Therefore, these mutant enzymes have strong similarity to arginyl-tRNA synthetase, glutaminyl-tRNA synthetase and glutamyl-tRNA synthetase in their mode of amino acid activation. The results suggest that an aaRS that does not normally require tRNA for amino acid activation can be switched to a tRNA-dependent mode.
authors.affiliation: State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 320 Yue-Yang Road, Shanghai 200031, China.
authors.forename: Li-Tao
authors.initials: LT
authors.lastname: Guo
authors.forename: Xiang-Long
authors.initials: XL
authors.lastname: Chen
authors.forename: Bo-Tao
authors.initials: BT
authors.lastname: Zhao
authors.forename: Yi
authors.initials: Y
authors.lastname: Shi
authors.forename: Wei
authors.initials: W
authors.lastname: Li
authors.forename: Hong
authors.initials: H
authors.lastname: Xue
authors.forename: You-Xin
authors.initials: YX
authors.lastname: Jin
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002417:Cattle; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D007532:Isoleucine / Q000737:chemistry; D008969:Molecular Sequence Data; D009154:Mutation; D011485:Protein Binding; D012364:RNA, Transfer, Trp / Q000378:metabolism*; D012545:Schiff Bases / Q000737:chemistry; D016415:Sequence Alignment; D014364:Tryptophan / Q000378:metabolism*; D014369:Tryptophan-tRNA Ligase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D014633:Valine / Q000737:chemistry* / Q000235:genetics
chemical_list: D012364:RNA, Transfer, Trp; D012545:Schiff Bases; D007532:Isoleucine; D014364:Tryptophan; D014369:Tryptophan-tRNA Ligase; C073175:WARS1 protein, human; D014633:Valine