Natural homolog of tRNA synthetase editing domain rescues conditional lethality caused by mistranslation.
AlaXp is a widely distributed (from bacteria to humans) genome-encoded homolog of the editing domain of alanyl-tRNA synthetases. Editing repairs the confusion of serine and glycine for alanine through clearance of mischarged (with Ser or Gly) tRNA(Ala). Because genome-encoded fragments of editing domains of other synthetases are scarce, the AlaXp redundancy of the editing domain of alanyl-tRNA synthetase is thought to reflect an unusual sensitivity of cells to mistranslation at codons for Ala. Indeed, a small defect in the editing activity of alanyl-tRNA synthetase is causally linked to neurodegeneration in the mouse. Although limited earlier studies demonstrated that AlaXp deacylated mischarged tRNA(Ala) in vitro, the significance of this activity in vivo has not been clear. Here we describe a bacterial system specifically designed to investigate activity of AlaXp in vivo. Serine toxicity, experienced by a strain harboring an editing-defective alanyl-tRNA synthetase, was rescued by an AlaXp-encoding transgene. Rescue was dependent on amino acid residues in AlaXp that are needed for its in vitro catalytic activity. Thus, the editing activity per se of AlaXp was essential for suppressing mistranslation. The results support the idea that the unique widespread distribution of AlaXp arises from the singular difficulties, for translation, poised by alanine.
Chong
Yeeting E
YE
Department of Molecular Biology, The Scripps Research Institute, La Jolla, California 92037, USA.
Yang
Xiang-Lei
XL
Schimmel
Paul
P
D000409:Alanine / Q000737:chemistry; D000595:Amino Acid Sequence; D000604:Amino Acyl-tRNA Synthetases / Q000378:metabolism*; D049148:Aminoacylation; D002384:Catalysis; D005816:Genetic Complementation Test; D008239:Lysine / Q000737:chemistry; D008954:Models, Biological; D008969:Molecular Sequence Data; D014176:Protein Biosynthesis; D017434:Protein Structure, Tertiary; D012343:RNA, Transfer / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D012694:Serine / Q000737:chemistry; D019076:Transgenes
D012694:Serine; D012343:RNA, Transfer; D000604:Amino Acyl-tRNA Synthetases; D008239:Lysine; D000409:Alanine