The transamidosome: a dynamic ribonucleoprotein particle dedicated to prokaryotic tRNA-dependent asparagine biosynthesis.
Asparagine, one of the 22 genetically encoded amino acids, can be synthesized by a tRNA-dependent mechanism. So far, this type of pathway was believed to proceed via two independent steps. A nondiscriminating aspartyl-tRNA synthetase (ND-DRS) first generates a mischarged aspartyl-tRNAAsn that dissociates from the enzyme and binds to a tRNA-dependent amidotransferase (AdT), which then converts the tRNA-bound aspartate into asparagine. We show herein that the ND-DRS, tRNAAsn, and AdT assemble into a specific ribonucleoprotein complex called transamidosome that remains stable during the overall catalytic process. Our results indicate that the tRNAAsn-mediated linkage between the ND-DRS and AdT enables channeling of the mischarged aspartyl-tRNAAsn intermediate between DRS and AdT active sites to prevent challenging of the genetic code integrity. We propose that formation of a ribonucleoprotein is a general feature for tRNA-dependent amino acid biosynthetic pathways that are remnants of earlier stages when amino acid synthesis and tRNA aminoacylation were coupled.
Bailly
Marc
M
UPR Architecture et Réactivité de l'ARN, Université Louis Pasteur de Strasbourg, CNRS, Institut de Biologie Moléculaire et Cellulaire, 15, Rue René Descartes, F-67084 Strasbourg Cédex, France.
Blaise
Mickaël
M
Lorber
Bernard
B
Becker
Hubert Dominique
HD
Kern
Daniel
D
D001216:Asparagine / Q000096:biosynthesis*; D001226:Aspartate-tRNA Ligase / Q000737:chemistry / Q000378:metabolism*; D002384:Catalysis; D007700:Kinetics; D046911:Macromolecular Substances / Q000378:metabolism; D008958:Models, Molecular; D008970:Molecular Weight; D019884:Nitrogenous Group Transferases / Q000737:chemistry / Q000378:metabolism*; D009690:Nucleic Acid Conformation; D011485:Protein Binding; D014176:Protein Biosynthesis; D011487:Protein Conformation; D012346:RNA, Transfer, Amino Acyl / Q000737:chemistry / Q000378:metabolism*; D012348:RNA, Transfer, Asn / Q000737:chemistry / Q000378:metabolism*; D012261:Ribonucleoproteins / Q000737:chemistry / Q000378:metabolism*; D016963:Thermus thermophilus / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*
D046911:Macromolecular Substances; D012346:RNA, Transfer, Amino Acyl; D012348:RNA, Transfer, Asn; D012261:Ribonucleoproteins; D001216:Asparagine; C412016:Asp-tRNA(Asn) amidotransferase; D019884:Nitrogenous Group Transferases; D001226:Aspartate-tRNA Ligase