title: Ribosome hijacking: a role for small protein B during trans-translation.
abstract: Tight recognition of codon-anticodon pairings by the ribosome ensures the accuracy and fidelity of protein synthesis. In eubacteria, translational surveillance and ribosome rescue are performed by the 'tmRNA-SmpB' system (transfer messenger RNA-small protein B). Remarkably, entry and accommodation of aminoacylated-tmRNA into stalled ribosomes occur without a codon-anticodon interaction but in the presence of SmpB. Here, we show that within a stalled ribosome, SmpB interacts with the three universally conserved bases G530, A1492 and A1493 that form the 30S subunit decoding centre, in which canonical codon-anticodon pairing occurs. The footprints at positions A1492 and A1493 of a small decoding centre, as well as on a set of conserved SmpB amino acids, were identified by nuclear magnetic resonance. Mutants at these residues display the same growth defects as for DeltasmpB strains. The SmpB protein has functional and structural similarities with initiation factor 1, and is proposed to be a functional mimic of the pairing between a codon and an anticodon.
authors.affiliation: Laboratoire de Cristallographie et RMN Biologiques, CNRS UMR 8015, Université Paris Descartes, 4, Avenue de l'Observatoire, 75006 Paris, France. sylvie.nonin@parisdescartes.fr
authors.forename: Sylvie
authors.initials: S
authors.lastname: Nonin-Lecomte
authors.forename: Noella
authors.initials: N
authors.lastname: Germain-Amiot
authors.forename: Reynald
authors.initials: R
authors.lastname: Gillet
authors.forename: Marc
authors.initials: M
authors.lastname: Hallier
authors.forename: Luc
authors.initials: L
authors.lastname: Ponchon
authors.forename: Frédéric
authors.initials: F
authors.lastname: Dardel
authors.forename: Brice
authors.initials: B
authors.lastname: Felden
mesh_terms: D000409:Alanine / Q000378:metabolism; D000926:Anticodon / Q000235:genetics; D003062:Codon / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000502:physiology*; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D009690:Nucleic Acid Conformation; D039861:Prokaryotic Initiation Factor-1 / Q000737:chemistry; D011485:Protein Binding; D011487:Protein Conformation; D025941:Protein Interaction Mapping; D012329:RNA, Bacterial / Q000737:chemistry / Q000502:physiology*; D012336:RNA, Ribosomal, 16S / Q000235:genetics / Q000378:metabolism; D012346:RNA, Transfer, Amino Acyl / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000502:physiology*; D012270:Ribosomes / Q000502:physiology*; D016963:Thermus thermophilus / Q000378:metabolism / Q000648:ultrastructure
chemical_list: D000926:Anticodon; D003062:Codon; D029968:Escherichia coli Proteins; D039861:Prokaryotic Initiation Factor-1; D012329:RNA, Bacterial; D012336:RNA, Ribosomal, 16S; D012346:RNA, Transfer, Amino Acyl; D016601:RNA-Binding Proteins; C430328:small protein B; C096222:tmRNA; D000409:Alanine