Poster abstracts

Poster number 67 submitted by Alexandra Kuzmishin

Quality control by trans-editing factor prevents global mistranslation of non-protein amino acid α-aminobutyrate

Alexandra B Kuzmishin (Department of Chemistry and Biochemistry and Center for RNA Biology, The Ohio State University, Columbus, Ohio 43210, USA.), Jo Marie Bacusmo, William A Cantara (Department of Chemistry and Biochemistry and Center for RNA Biology, The Ohio State University, Columbus, Ohio 43210, USA.), Yuki Goto, Hiroaki Suga (Department of Chemistry, Graduate School of Science, The University of Tokyo, Bunkyo, Tokyo 113-0033, Japan), Karin Musier-Forsyth (Department of Chemistry and Biochemistry and Center for RNA Biology, The Ohio State University, Columbus, Ohio 43210, USA.)

Abstract:
Accuracy in protein biosynthesis is maintained through multiple pathways, with a critical checkpoint occurring at the tRNA aminoacylation step catalyzed by aminoacyl-tRNA synthetases (AARSs). In addition to Ala-tRNAPro editing mediated by the insertion (INS) domain present in most bacterial prolyl-tRNA synthetases (ProRS), single-domain trans-editing factors structurally homologous to INS are present in some organisms. To date, INS-like editing proteins have been shown to act on specific tRNAs that are mischarged with genetically encoded amino acids. However, structurally related non-protein amino acids are ubiquitous in cells and threaten the proteome. Here, we show that Rhodopseudomonas palustris ProXp-x, a previously uncharacterized INS homolog, edits a known ProRS aminoacylation error, Ala-tRNAPro, but displays even more robust editing of tRNAs misaminoacylated with the non-protein amino acid α-aminobutyrate (Abu) in vitro and in vivo. Abu is the product of the transamination of oxobutyrate, a metabolite in Ile biosynthesis, and a precursor metabolite in Thr biosynthesis. Abu is mischarged by E. coli ValRS and ProRS in vitro, and in vivo experiments showed that Abu is toxic to an E. coli strain encoding an editing-defective ValRS (1). However, expression of R. palustris ProXp-x rescues cell growth, presumably by removing Abu that has been mischarged onto tRNAVal by the editing-deficient ValRS. Our results indicate that editing by trans-editing domains such as ProXp-x studied here may offer advantages to cells, especially under environmental conditions where concentrations of non-protein amino acids may challenge the substrate specificity of AARSs.

References:
1. Döring V, Mootz HD, Nangle LA, Hendrickson TL, de Crécy-Lagard V, Schimmel P, Marlière P. Enlarging the amino acid set of Escherichia coli by infiltration of the valine coding pathway. Science. 2001 April 20; 292:501-4.

Keywords: aminoacyl-tRNA synthetase, trans-editing, Rhodopseudomonas palustris