Poster abstracts
Poster number 52 submitted by Lexie Kuzmishin
Quality control by trans-editing factor prevents global mistranslation of non-protein amino acid alpha-aminobutyrate
Lexie Kuzmishin (The Ohio State Biochemistry Program, Department of Chemistry and Biochemistry, and Center for RNA Biology, The Ohio State University), William Cantara (Department of Chemistry and Biochemistry, and Center for RNA Biology, The Ohio State University), Jo Marie Bacusmo (Department of Chemistry and Biochemistry, and Center for RNA Biology, The Ohio State University), Karin Musier-Forsyth (The Ohio State Biochemistry Program, Department of Chemistry and Biochemistry, and Center for RNA Biology, The Ohio State University)
Abstract:
Aminoacyl-tRNA synthetases attach cognate amino acids to tRNAs, and are a critical checkpoint in protein synthesis. ARSs misactivate amino acids that are similar to their cognate substrates; thus, aminoacyl-tRNA editing mechanisms are needed to prevent widespread mistranslation. 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 trans-editing proteins have been shown to act on tRNAs mischarged with proteogenic amino acids. Here, we show that Rhodopseudomonas palustris ProXp-x, a previously uncharacterized INS homolog, displays robust editing of tRNAPro and tRNAVal mischarged with the non-protein amino acid α-aminobutyrate (2-Abu) in vitro. 2-Abu is the product of the transamination of oxobutyrate, a metabolite in Ile biosynthesis, and is a precursor metabolite in Thr biosynthesis. 2-Abu is mischarged by E. coli ValRS and ProRS in vitro. In vivo experiments showed that 2-Abu is toxic to an E. coli strain encoding an editing-defective ValRS. However, expression of R. palustris ProXp-x rescues cell growth, presumably by removing 2-Abu that has been mischarged onto tRNAVal by the editing-deficient ValRS. We hypothesize that ProXp-x serves as a general 2-Abu-tRNA deacylase to prevent accumulation of this species under growth conditions wherein cellular 2-Abu concentrations are high. A R. palustris ProXp-x deletion strain has been constructed, and experiments are underway to identify the environmental stresses that impart a growth defect in the null strain.
Keywords: trans-editing, aminoacyl-tRNA synthetases, Rhodopseudomonas palustris