SecM-stalled ribosomes adopt an altered geometry at the peptidyl transferase center

Autor: Birgit Seidelt, Shashi Bhushan, Jens Frauenfeld, Thomas Hoffmann, Thorsten Mielke, Otto Berninghausen, Roland Beckmann, Daniel N. Wilson
Jazyk: angličtina
Rok vydání: 2011
Předmět:
Peptidyl transferase
QH301-705.5
Molecular Conformation
Ribosome
General Biochemistry
Genetics and Molecular Biology
Biophysics/Macromolecular Assemblies and Machines
RNA
Transfer
23S ribosomal RNA
Large ribosomal subunit
Molecular Biology/Translational Regulation
Catalytic Domain
Escherichia coli
Biochemistry/RNA Structure
Biology (General)
Protein Structure
Quaternary
Ribosome-nascent chain complex
Biophysics/Transcription and Translation
Cell Biology/Gene Expression
General Immunology and Microbiology
biology
General Neuroscience
Escherichia coli Proteins
Cryoelectron Microscopy
Ribosomal RNA
Cell biology
Biophysics/RNA Structure
Protein Structure
Tertiary
Biochemistry
Protein Biosynthesis
Transfer RNA
Peptidyl Transferases
biology.protein
Translational elongation
Molecular Biology/RNA-Protein Interactions
General Agricultural and Biological Sciences
Biochemistry/Transcription and Translation
Ribosomes
Research Article
Molecular Biology/Translation Mechanisms
Transcription Factors
Zdroj: PLoS Biology, Vol 9, Iss 1, p e1000581 (2011)
PLoS Biology
ISSN: 1545-7885
1544-9173
Popis: A structure of a ribosome stalled during translation of the SecM peptide provides insight into the mechanism by which the large subunit active site is inactivated.
As nascent polypeptide chains are synthesized, they pass through a tunnel in the large ribosomal subunit. Interaction between specific nascent chains and the ribosomal tunnel is used to induce translational stalling for the regulation of gene expression. One well-characterized example is the Escherichia coli SecM (secretion monitor) gene product, which induces stalling to up-regulate translation initiation of the downstream secA gene, which is needed for protein export. Although many of the key components of SecM and the ribosomal tunnel have been identified, understanding of the mechanism by which the peptidyl transferase center of the ribosome is inactivated has been lacking. Here we present a cryo-electron microscopy reconstruction of a SecM-stalled ribosome nascent chain complex at 5.6 Å. While no cascade of rRNA conformational changes is evident, this structure reveals the direct interaction between critical residues of SecM and the ribosomal tunnel. Moreover, a shift in the position of the tRNA–nascent peptide linkage of the SecM-tRNA provides a rationale for peptidyl transferase center silencing, conditional on the simultaneous presence of a Pro-tRNAPro in the ribosomal A-site. These results suggest a distinct allosteric mechanism of regulating translational elongation by the SecM stalling peptide.
Author Summary In all cells, ribosomes perform the job of making proteins. As the proteins are synthesized they pass through a tunnel in the ribosome, and some growing proteins interact with the tunnel, leading to stalling of protein synthesis. Here, we used cryo-electron microscopy to determine the structure of a ribosome stalled during the translation of the Escherichia coli secretion monitor (SecM) polypeptide chain. The structure reveals the path of the SecM peptide through the tunnel as well as the sites of interaction with the tunnel components. Interestingly, the structure shows a shift in the position of the transfer RNA (tRNA) to which the growing SecM polypeptide chain is attached. Since peptide bond formation during protein synthesis requires precise placement of the substrates, namely, the peptidyl-tRNA and the incoming amino acyl-tRNA, it is proposed that this shift in the SecM-tRNA explains why peptide bond formation cannot occur and translation stalls.
Databáze: OpenAIRE
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