Spontaneous formation of the unlocked state of the ribosome is a multistep process

The mechanism of substrate translocation through the ribosome is central to the rapid and faithful translation of mRNA into proteins. The rate-limiting step in translocation is an unlocking process that includes the formation of an "unlocked" intermediate state, which requires the converge...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2010-01, Vol.107 (2), p.709-714
Main Authors: Munro, James B, Altman, Roger B, Tung, Chang-Shung, Cate, Jamie H.D, Sanbonmatsu, Kevin Y, Blanchard, Scott C
Format: Article
Language:English
Subjects:
Biological Sciences
Cells
Conserved Sequence
Fluorescence
Fluorescence Resonance Energy Transfer
GTP Phosphohydrolases - genetics
GTP Phosphohydrolases - metabolism
Hybridity
Imaging
Kinetics
Messenger RNA
Models, Molecular
Molecular structure
Molecules
Nucleic Acid Hybridization
Physiological regulation
Protein Biosynthesis
Protein Conformation
Proteins
Proteins - chemistry
Proteins - genetics
Renovations
Ribosomes
Ribosomes - genetics
Ribosomes - metabolism
Ribosomes - ultrastructure
RNA, Messenger - genetics
RNA, Transfer - genetics
RNA, Transfer, Met - chemistry
Trajectories
Transfer RNA
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Summary:The mechanism of substrate translocation through the ribosome is central to the rapid and faithful translation of mRNA into proteins. The rate-limiting step in translocation is an unlocking process that includes the formation of an "unlocked" intermediate state, which requires the convergence of large-scale conformational events within the ribosome including tRNA hybrid states formation, closure of the ribosomal L1 stalk domain, and subunit ratcheting. Here, by imaging of the pretranslocation ribosome complex from multiple structural perspectives using two- and three-color single-molecule fluorescence resonance energy transfer, we observe that tRNA hybrid states formation and L1 stalk closure, events central to the unlocking mechanism, are not tightly coupled. These findings reveal that the unlocked state is achieved through a stochastic-multistep process, where the extent of conformational coupling depends on the nature of tRNA substrates. These data suggest that cellular mechanisms affecting the coupling of conformational processes on the ribosome may regulate the process of translation elongation.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.0908597107