Allosteric vs. spontaneous exit-site (E-site) tRNA dissociation early in protein synthesis

During protein synthesis, deacylated transfer RNAs leave the ribosome via an exit (E) site after mRNA translocation. How the ribosome regulates tRNA dissociation and whether functional linkages between the aminoacyl (A) and E sites modulate the dynamics of protein synthesis have long been debated. U...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2011-10, Vol.108 (41), p.16980-16985
Main Authors: Chen, Chunlai, Stevens, Benjamin, Kaur, Jaskiran, Smilansky, Zeev, Cooperman, Barry S, Goldman, Yale E
Format: Article
Language:English
Subjects:
Allosteric properties
Allosteric Site
Amino Acid Sequence
Base Sequence
Biological Sciences
Biological Transport, Active
Biophysical Phenomena
Codons
Communication
Correlation analysis
Correlations
Cycle protein
dissociation
Elongation
energy transfer
Fluorescence
Fluorescence Resonance Energy Transfer
Kinetics
Lasers
Messenger RNA
Molecular Sequence Data
Molecules
mRNA
Nucleic Acid Conformation
Peptide Chain Elongation, Translational - physiology
Protein biosynthesis
Protein Biosynthesis - physiology
Protein synthesis
Protein transport
Ribosomes
Ribosomes - metabolism
RNA, Messenger - genetics
RNA, Messenger - metabolism
RNA, Transfer - chemistry
RNA, Transfer - metabolism
Transfer RNA
Translocation
tRNA
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Summary:During protein synthesis, deacylated transfer RNAs leave the ribosome via an exit (E) site after mRNA translocation. How the ribosome regulates tRNA dissociation and whether functional linkages between the aminoacyl (A) and E sites modulate the dynamics of protein synthesis have long been debated. Using single molecule fluorescence resonance energy transfer experiments, we find that, during early cycles of protein elongation, tRNAs are often held in the E site until being allosterically released when the next aminoacyl tRNA binds to the A site. This process is regulated by the length and sequence of the nascent peptide and by the conformational state, detected by tRNA proximity, prior to translocation. In later cycles, E-site tRNA dissociates spontaneously. Our results suggest that the distribution of pretranslocation tRNA states and posttranslocation pathways are correlated within each elongation cycle via communication between distant subdomains in the ribosome, but that this correlation between elongation cycle intermediates does not persist into succeeding cycles.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.1106999108