Structural insight into nascent polypeptide chain-mediated translational stalling.
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.
Seidelt
Birgit
B
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.
Innis
C Axel
CA
Wilson
Daniel N
DN
Gartmann
Marco
M
Armache
Jean-Paul
JP
Villa
Elizabeth
E
Trabuco
Leonardo G
LG
Becker
Thomas
T
Mielke
Thorsten
T
Schulten
Klaus
K
Steitz
Thomas A
TA
Beckmann
Roland
R
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*
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