Visualization of two transfer RNAs trapped in transit during elongation factor G-mediated translocation.
Proc Natl Acad Sci U S A
; 110(52): 20964-9, 2013 Dec 24.
Article
in En
| MEDLINE
| ID: mdl-24324168
ABSTRACT
During protein synthesis, coupled translocation of messenger RNAs (mRNA) and transfer RNAs (tRNA) through the ribosome takes place following formation of each peptide bond. The reaction is facilitated by large-scale conformational changes within the ribosomal complex and catalyzed by elongtion factor G (EF-G). Previous structural analysis of the interaction of EF-G with the ribosome used either model complexes containing no tRNA or only a single tRNA, or complexes where EF-G was directly bound to ribosomes in the posttranslocational state. Here, we present a multiparticle cryo-EM reconstruction of a translocation intermediate containing two tRNAs trapped in transit, bound in chimeric intrasubunit ap/P and pe/E hybrid states. The downstream ap/P-tRNA is contacted by domain IV of EF-G and P-site elements within the 30S subunit body, whereas the upstream pe/E-tRNA maintains tight interactions with P-site elements of the swiveled 30S head. Remarkably, a tight compaction of the tRNA pair can be seen in this state. The translocational intermediate presented here represents a previously missing link in understanding the mechanism of translocation, revealing that the ribosome uses two distinct molecular ratchets, involving both intra- and intersubunit rotational movements, to drive the synchronous movement of tRNAs and mRNA.
Key words
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Peptide Chain Elongation, Translational
/
Ribosomes
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RNA, Messenger
/
Models, Molecular
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Peptide Elongation Factor G
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Nucleic Acid Conformation
Type of study:
Prognostic_studies
Language:
En
Journal:
Proc Natl Acad Sci U S A
Year:
2013
Document type:
Article
Affiliation country: