title: A tRNA-independent mechanism for transamidosome assembly promotes aminoacyl-tRNA transamidation.
abstract: Many bacteria lack genes encoding asparaginyl- and/or glutaminyl-tRNA synthetase and consequently rely on an indirect path for the synthesis of both Asn-tRNA(Asn) and Gln-tRNA(Gln). In some bacteria such as Thermus thermophilus, efficient delivery of misacylated tRNA to the downstream amidotransferase (AdT) is ensured by formation of a stable, tRNA-dependent macromolecular complex called the Asn-transamidosome. This complex enables direct delivery of Asp-tRNA(Asn) from the non-discriminating aspartyl-tRNA synthetase to AdT, where it is converted into Asn-tRNA(Asn). Previous characterization of the analogous Helicobacter pylori Asn-transamidosome revealed that it is dynamic and cannot be stably isolated, suggesting the possibility of an alternative mechanism to facilitate assembly of a stable complex. We have identified a novel protein partner called Hp0100 as a component of a stable, tRNA-independent H. pylori Asn-transamidosome; this complex contains a non-discriminating aspartyl-tRNA synthetase, AdT, and Hp0100 but does not require tRNA(Asn) for assembly. Hp0100 also enhances the capacity of AdT to convert Asp-tRNA(Asn) into Asn-tRNA(Asn) by ∼35-fold. Our results demonstrate that bacteria have adopted multiple divergent methods for transamidosome assembly and function.
authors.affiliation: Department of Chemistry, Wayne State University, Detroit, Michigan 48230, USA.
authors.forename: Gayathri N
authors.initials: GN
authors.lastname: Silva
authors.forename: Shirin
authors.initials: S
authors.lastname: Fatma
authors.forename: Ashley M
authors.initials: AM
authors.lastname: Floyd
authors.forename: Frederic
authors.initials: F
authors.lastname: Fischer
authors.forename: Pitak
authors.initials: P
authors.lastname: Chuawong
authors.forename: Amanda N
authors.initials: AN
authors.lastname: Cruz
authors.forename: Rachel M
authors.initials: RM
authors.lastname: Simari
authors.forename: Nilesh
authors.initials: N
authors.lastname: Joshi
authors.forename: Daniel
authors.initials: D
authors.lastname: Kern
authors.forename: Tamara L
authors.initials: TL
authors.lastname: Hendrickson
mesh_terms: D000579:Amidinotransferases / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D016480:Helicobacter pylori / Q000201:enzymology* / Q000235:genetics; D009097:Multienzyme Complexes / Q000235:genetics / Q000378:metabolism*; D012329:RNA, Bacterial / Q000235:genetics / Q000378:metabolism*; D012346:RNA, Transfer, Amino Acyl / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D009097:Multienzyme Complexes; D012329:RNA, Bacterial; D012346:RNA, Transfer, Amino Acyl; D000579:Amidinotransferases