Magnesium ion-mediated binding to tRNA by an amino-terminal peptide of a class II tRNA synthetase.
Aspartyl-tRNA synthetase is a class II tRNA synthetase and occurs in a multisynthetase complex in mammalian cells. Human Asp-tRNA synthetase contains a short 32-residue amino-terminal extension that can control the release of charged tRNA and its direct transfer to elongation factor 1 alpha; however, whether the extension binds to tRNA directly or interacts with the synthetase active site is not known. Full-length human AspRS, but not amino-terminal 32 residue-deleted, fully active AspRS, was found to bind to noncognate tRNA(fMet) in the presence of Mg(2+). Synthetic amino-terminal peptides bound similarly to tRNA(fMet), whereas little or no binding of polynucleotides, poly(dA-dT), or polyphosphate to the peptides was found. The apparent binding constants to tRNA by the peptide increased with increasing concentrations of Mg(2+), suggesting Mg(2+) mediates the binding as a new mode of RNA.peptide interactions. The binding of tRNA(fMet) to amino-terminal peptides was also observed using fluorescence-labeled tRNAs and circular dichroism. These results suggest that a small peptide can bind to tRNA selectively and that evolution of class II tRNA synthetases may involve structural changes of amino-terminal extensions for enhanced selective binding of tRNA.
Hammamieh
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Department of Chemistry, Georgetown University, Washington, DC 20057, USA.
Yang
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D000595:Amino Acid Sequence; D001226:Aspartate-tRNA Ligase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D002942:Circular Dichroism; D006801:Humans; D008274:Magnesium / Q000378:metabolism*; D015636:Magnesium Chloride / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012358:RNA, Transfer, Met / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000378:metabolism; D017384:Sequence Deletion; D013050:Spectrometry, Fluorescence; D014443:Tyrosine / Q000737:chemistry
D010446:Peptide Fragments; D012358:RNA, Transfer, Met; D016601:RNA-Binding Proteins; C024988:tRNA, formylmethionine-; D015636:Magnesium Chloride; D014443:Tyrosine; D001226:Aspartate-tRNA Ligase; D008274:Magnesium