title: Riboswitch (T-box)-mediated control of tRNA-dependent amidation in Clostridium acetobutylicum rationalizes gene and pathway redundancy for asparagine and asparaginyl-trnaasn synthesis.
abstract: Analysis of the Gram-positive Clostridium acetobutylicum genome reveals an inexplicable level of redundancy for the genes putatively involved in asparagine (Asn) and Asn-tRNA(Asn) synthesis. Besides a duplicated set of gatCAB tRNA-dependent amidotransferase genes, there is a triplication of aspartyl-tRNA synthetase genes and a duplication of asparagine synthetase B genes. This genomic landscape leads to the suspicion of the incoherent simultaneous use of the direct and indirect pathways of Asn and Asn-tRNA(Asn) formation. Through a combination of biochemical and genetic approaches, we show that C. acetobutylicum forms Asn and Asn-tRNA(Asn) by tRNA-dependent amidation. We demonstrate that an entire transamidation pathway composed of aspartyl-tRNA synthetase and one set of GatCAB genes is organized as an operon under the control of a tRNA(Asn)-dependent T-box riboswitch. Finally, our results suggest that this exceptional gene redundancy might be interconnected to control tRNA-dependent Asn synthesis, which in turn might be involved in controlling the metabolic switch from acidogenesis to solventogenesis in C. acetobutylicum.
authors.affiliation: Unité Mixte de Recherche "Génétique Moléculaire, Génomique, Microbiologie," CNRS, Université de Strasbourg, 21 rue René Descartes, 67084 Strasbourg, France.
authors.forename: Nizar Y
authors.initials: NY
authors.lastname: Saad
authors.forename: Bettina
authors.initials: B
authors.lastname: Schiel
authors.forename: Mélanie
authors.initials: M
authors.lastname: Brayé
authors.forename: John T
authors.initials: JT
authors.lastname: Heap
authors.forename: Nigel P
authors.initials: NP
authors.lastname: Minton
authors.forename: Peter
authors.initials: P
authors.lastname: Dürre
authors.forename: Hubert Dominique
authors.initials: HD
authors.lastname: Becker
mesh_terms: D001216:Asparagine / Q000096:biosynthesis* / Q000235:genetics; D001217:Aspartate-Ammonia Ligase / Q000096:biosynthesis* / Q000235:genetics; D001426:Bacterial Proteins / Q000096:biosynthesis* / Q000235:genetics; D046969:Clostridium acetobutylicum / Q000235:genetics / Q000378:metabolism*; D012329:RNA, Bacterial / Q000235:genetics / Q000378:metabolism*; D012346:RNA, Transfer, Amino Acyl / Q000096:biosynthesis* / Q000235:genetics; D058928:Riboswitch / Q000502:physiology*
chemical_list: D001426:Bacterial Proteins; D012329:RNA, Bacterial; D012346:RNA, Transfer, Amino Acyl; D058928:Riboswitch; D001216:Asparagine; D001217:Aspartate-Ammonia Ligase