Loss of editing activity during the evolution of mitochondrial phenylalanyl-tRNA synthetase.
Accurate selection of amino acids is essential for faithful translation of the genetic code. Errors during amino acid selection are usually corrected by the editing activity of aminoacyl-tRNA synthetases such as phenylalanyl-tRNA synthetases (PheRS), which edit misactivated tyrosine. Comparison of cytosolic and mitochondrial PheRS from the yeast Saccharomyces cerevisiae suggested that the organellar protein might lack the editing activity. Yeast cytosolic PheRS was found to contain an editing site, which upon disruption abolished both cis and trans editing of Tyr-tRNA(Phe). Wild-type mitochondrial PheRS lacked cis and trans editing and could synthesize Tyr-tRNA(Phe), an activity enhanced in active site variants with improved tyrosine recognition. Possible trans editing was investigated in isolated mitochondrial extracts, but no such activity was detected. These data indicate that the mitochondrial protein synthesis machinery lacks the tyrosine proofreading activity characteristic of cytosolic translation. This difference between the mitochondria and the cytosol suggests that either organellar protein synthesis quality control is focused on another step or that translation in this compartment is inherently less accurate than in the cytosol.
Roy
Hervé
H
Department of Microbiology, The Ohio State University, Columbus, Ohio 43210-1292, USA.
Ling
Jiqiang
J
Alfonzo
Juan
J
Ibba
Michael
M
D000255:Adenosine Triphosphate / Q000737:chemistry; D000595:Amino Acid Sequence; D001665:Binding Sites; D003600:Cytosol / Q000378:metabolism; D012321:DNA-Directed RNA Polymerases / Q000737:chemistry; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000378:metabolism; D019143:Evolution, Molecular; D007700:Kinetics; D008928:Mitochondria / Q000201:enzymology* / Q000378:metabolism; D008954:Models, Biological; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D010649:Phenylalanine / Q000737:chemistry; D010652:Phenylalanine-tRNA Ligase / Q000737:chemistry*; D010710:Phosphates / Q000737:chemistry; D010802:Phylogeny; D010957:Plasmids / Q000378:metabolism; D017354:Point Mutation; D014176:Protein Biosynthesis; D017393:RNA Editing; D012343:RNA, Transfer / Q000737:chemistry; D012270:Ribosomes / Q000502:physiology*; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D013997:Time Factors; D014158:Transcription, Genetic; D014443:Tyrosine / Q000737:chemistry; D014764:Viral Proteins / Q000737:chemistry
D010710:Phosphates; D014764:Viral Proteins; D014443:Tyrosine; D010649:Phenylalanine; D000255:Adenosine Triphosphate; D012343:RNA, Transfer; C062210:bacteriophage T7 RNA polymerase; D012321:DNA-Directed RNA Polymerases; D010652:Phenylalanine-tRNA Ligase