70S-scanning initiation is a novel and frequent initiation mode of ribosomal translation in bacteria

Hiroshi Yamamoto, Daniela Wittek, Romi Gupta, Bo Qin, Takuya Ueda, Roland Krause, Kaori Yamamoto, Renate Albrecht, Markus Pech*, Knud H. Nierhaus

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

67 Citations (Scopus)


According to the standard model of bacterial translation initiation, the small ribosomal 30S subunit binds to the initiation site of an mRNA with the help of three initiation factors (IF1-IF3). Here, we describe a novel type of initiation termed "70S-scanning initiation," where the 70S ribosome does not necessarily dissociate after translation of a cistron, but rather scans to the initiation site of the downstream cistron. We detailed the mechanism of 70S-scanning initiation by designing unique monocistronic and polycistronic mRNAs harboring translation reporters, and by reconstituting systems to characterize each distinct mode of initiation. Results show that 70S scanning is triggered by fMet-tRNA and does not require energy; the Shine-Dalgarno sequence is an essential recognition element of the initiation site. IF1 and IF3 requirements for the various initiation modes were assessed by the formation of productive initiation complexes leading to synthesis of active proteins. IF3 is essential and IF1 is highly stimulating for the 70S-scanning mode. The task of IF1 appears to be the prevention of untimely interference by ternary aminoacyl (aa)-tRNA•elongation factor thermo unstable (EF-Tu)•GTP complexes. Evidence indicates that at least 50% of bacterial initiation events use the 70S-scanning mode, underscoring the relative importance of this translation initiation mechanism.

Original languageEnglish
Pages (from-to)E1180-E1189
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number9
Publication statusPublished - 2016 Mar 1
Externally publishedYes


  • 30S-binding initiation
  • 70S-scanning initiation
  • Protein synthesis
  • Ribosomal functions
  • Translational initiation

ASJC Scopus subject areas

  • General


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