A tRNA-independent mechanism for transamidosome assembly promotes aminoacyl-tRNA transamidation

J Biol Chem. 2013 Feb 8;288(6):3816-22. doi: 10.1074/jbc.M112.441394. Epub 2012 Dec 20.

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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amidinotransferases / genetics
  • Amidinotransferases / metabolism*
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism*
  • Helicobacter pylori / enzymology*
  • Helicobacter pylori / genetics
  • Multienzyme Complexes / genetics
  • Multienzyme Complexes / metabolism*
  • RNA, Bacterial / genetics
  • RNA, Bacterial / metabolism*
  • RNA, Transfer, Amino Acyl / genetics
  • RNA, Transfer, Amino Acyl / metabolism*

Substances

  • Bacterial Proteins
  • Multienzyme Complexes
  • RNA, Bacterial
  • RNA, Transfer, Amino Acyl
  • Amidinotransferases