Elucidation of tRNA-dependent editing by a class II tRNA synthetase and significance for cell viability.
Editing of misactivated amino acids by class I tRNA synthetases is encoded by a specialized internal domain specific to class I enzymes. In contrast, little is known about editing activities of the structurally distinct class II enzymes. Here we show that the class II alanyl-tRNA synthetase (AlaRS) has a specialized internal domain that appears weakly related to an appended domain of threonyl-tRNA synthetase (ThrRS), but is unrelated to that found in class I enzymes. Editing of misactivated glycine or serine was shown to require a tRNA cofactor. Specific mutations in the aforementioned domain disrupt editing and lead to production of mischarged tRNA. This class-specific editing domain was found to be essential for cell growth, in the presence of elevated concentrations of glycine or serine. In contrast to ThrRS, where the editing domain is not found in all three kingdoms of living organisms, it was incorporated early into AlaRSs and is present throughout evolution. Thus, tRNA-dependent editing by AlaRS may have been critical for making the genetic code sufficiently accurate to generate the tree of life.
Beebe
Kirk
K
The Skaggs Institute for Chemical Biology, The Scripps Research Institute, Beckman Center, BCC379, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.
Ribas De Pouplana
Lluis
L
Schimmel
Paul
P
D000255:Adenosine Triphosphate / Q000378:metabolism; D000412:Alanine-tRNA Ligase / Q000145:classification / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D002470:Cell Survival; D019143:Evolution, Molecular; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010641:Phenotype; D010802:Phylogeny; D017354:Point Mutation; D017434:Protein Structure, Tertiary; D017393:RNA Editing; D012343:RNA, Transfer / Q000378:metabolism*; D016415:Sequence Alignment; D013914:Threonine-tRNA Ligase / Q000378:metabolism
D000255:Adenosine Triphosphate; D012343:RNA, Transfer; D013914:Threonine-tRNA Ligase; D000412:Alanine-tRNA Ligase