Stefano Marzi / Alexander G Myasnikov / Alexander Serganov / Chantal Ehresmann / Pascale Romby / Marat Yusupov / Bruno P Klaholz /
PubMed Abstract
Gene expression can be regulated at the level of initiation of protein biosynthesis via structural elements present at the 5' untranslated region of mRNAs. These folded mRNA segments may bind to the ...Gene expression can be regulated at the level of initiation of protein biosynthesis via structural elements present at the 5' untranslated region of mRNAs. These folded mRNA segments may bind to the ribosome, thus blocking translation until the mRNA unfolds. Here, we report a series of cryo-electron microscopy snapshots of ribosomal complexes directly visualizing either the mRNA structure blocked by repressor protein S15 or the unfolded, active mRNA. In the stalled state, the folded mRNA prevents the start codon from reaching the peptidyl-tRNA (P) site inside the ribosome. Upon repressor release, the mRNA unfolds and moves into the mRNA channel allowing translation initiation. A comparative structure and sequence analysis suggests the existence of a universal stand-by site on the ribosome (the 30S platform) dedicated for binding regulatory 5' mRNA elements. Different types of mRNA structures may be accommodated during translation preinitiation and regulate gene expression by transiently stalling the ribosome.
EMDB-1391: Structured mRNAs regulate translation initiation by binding to the platform of the ribosome. PDB-2vaz: Model of the S15-mRNA complex fitted into the cryo-EM map of the 70S entrapment complex. Method: EM (single particle) / Resolution: 10.0 Å
Source
escherichia coli (E. coli)
Keywords
TRANSLATION / PLATFORM-BINDING CENTER / GENE EXPRESSION REGULATION / RIBOSOMAL PROTEIN / RIBONUCLEOPROTEIN / PROTEIN SYNTHESIS / TRANSLATION INITIATION / RIBOSOME / RIBOSWITCH / RNA-BINDING / RRNA-BINDING / RNA PSEUDOKNOT / MRNA STRUCTURE / REPRESSOR PROTEIN
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TRANSLATION / PLATFORM-BINDING CENTER / GENE EXPRESSION REGULATION / 
