Transiently misacylated tRNA is a primer for editing of misactivated adenylates by class I aminoacyl-tRNA synthetases.
The genetic code depends on amino acid fine structure discrimination by aminoacyl-tRNA synthetases. For isoleucyl- (IleRS) and valyl-tRNA synthetases (ValRS), reactions that hydrolyze misactivated noncognate amino acids help to achieve high accuracy in aminoacylation. Two editing pathways contribute to aminoacylation fidelity: pretransfer and post-transfer. In pretransfer editing, the misactivated amino acid is hydrolyzed as an aminoacyl adenylate, while in post-transfer editing a misacylated tRNA is deacylated. Both reactions are dependent on a tRNA cofactor and require translocation to a site located approximately 30 A from the site of amino acid activation. Using a series of 3'-end modified tRNAs that are deficient in either aminoacylation, deacylation, or both, total editing (the sum of pre- and post-transfer editing) was shown to require both aminoacylation and deacylation activities. These and additional results with IleRS are consistent with a post-transfer deacylation event initiating formation of an editing-active enzyme/tRNA complex. In this state, the primed complex processively edits misactivated valyl-adenylate via the pretransfer route. Thus, misacylated tRNA is an obligatory intermediate for editing by either pathway.
The Skaggs Institute for Chemical Biology and Department of Molecular Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, USA.
Brian E
BE
Nordin
Paul
P
Schimmel
D024509:3' Flanking Region; D000215:Acylation; D000227:Adenine Nucleotides / Q000737:chemistry; D000251:Adenosine Triphosphatases / Q000737:chemistry; D029968:Escherichia coli Proteins / Q000737:chemistry; D006868:Hydrolysis; D007533:Isoleucine-tRNA Ligase / Q000737:chemistry*; D017393:RNA Editing; D012329:RNA, Bacterial / Q000737:chemistry; D012346:RNA, Transfer, Amino Acyl / Q000737:chemistry*; D013379:Substrate Specificity; D014637:Valine-tRNA Ligase / Q000737:chemistry*
D000227:Adenine Nucleotides; D029968:Escherichia coli Proteins; D012329:RNA, Bacterial; D012346:RNA, Transfer, Amino Acyl; D000251:Adenosine Triphosphatases; D007533:Isoleucine-tRNA Ligase; D014637:Valine-tRNA Ligase