title: Structural insight into nascent polypeptide chain-mediated translational stalling.
abstract: Expression of the Escherichia coli tryptophanase operon depends on ribosome stalling during translation of the upstream TnaC leader peptide, a process for which interactions between the TnaC nascent chain and the ribosomal exit tunnel are critical. We determined a 5.8 angstrom-resolution cryo-electron microscopy and single-particle reconstruction of a ribosome stalled during translation of the tnaC leader gene. The nascent chain was extended within the exit tunnel, making contacts with ribosomal components at distinct sites. Upon stalling, two conserved residues within the peptidyltransferase center adopted conformations that preclude binding of release factors. We propose a model whereby interactions within the tunnel are relayed to the peptidyltransferase center to inhibit translation. Moreover, we show that nascent chains adopt distinct conformations within the ribosomal exit tunnel.
authors.affiliation: Gene Center and Center for Integrated Protein Science Munich (CIPSM), Department for Chemistry and Biochemistry, University of Munich, Feodor-Lynen-Strasse 25, 81377 Munich, Germany.
authors.forename: Birgit
authors.initials: B
authors.lastname: Seidelt
authors.forename: C Axel
authors.initials: CA
authors.lastname: Innis
authors.forename: Daniel N
authors.initials: DN
authors.lastname: Wilson
authors.forename: Marco
authors.initials: M
authors.lastname: Gartmann
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Armache
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Villa
authors.forename: Leonardo G
authors.initials: LG
authors.lastname: Trabuco
authors.forename: Thomas
authors.initials: T
authors.lastname: Becker
authors.forename: Thorsten
authors.initials: T
authors.lastname: Mielke
authors.forename: Klaus
authors.initials: K
authors.lastname: Schulten
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Steitz
authors.forename: Roland
authors.initials: R
authors.lastname: Beckmann
mesh_terms: D001665:Binding Sites; D020285:Cryoelectron Microscopy; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D015964:Gene Expression Regulation, Bacterial; D007091:Image Processing, Computer-Assisted; D008954:Models, Biological; D008958:Models, Molecular; D009876:Operon; D010458:Peptidyl Transferases / Q000378:metabolism; D014176:Protein Biosynthesis; D011487:Protein Conformation; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure; D012269:Ribosomal Proteins / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure; D012270:Ribosomes / Q000378:metabolism* / Q000648:ultrastructure; D014368:Tryptophanase / Q000096:biosynthesis / Q000235:genetics*
chemical_list: D029968:Escherichia coli Proteins; D016601:RNA-Binding Proteins; D012269:Ribosomal Proteins; C489371:rplV protein, E coli; C081473:tnaC protein, E coli; D010458:Peptidyl Transferases; D014368:Tryptophanase