Structural basis of transcription-translation coupling

Science. 2020 Sep 11;369(6509):1359-1365. doi: 10.1126/science.abb5317. Epub 2020 Aug 20.


In bacteria, transcription and translation are coupled processes in which the movement of RNA polymerase (RNAP)-synthesizing messenger RNA (mRNA) is coordinated with the movement of the first ribosome-translating mRNA. Coupling is modulated by the transcription factors NusG (which is thought to bridge RNAP and the ribosome) and NusA. Here, we report cryo-electron microscopy structures of Escherichia coli transcription-translation complexes (TTCs) containing different-length mRNA spacers between RNAP and the ribosome active-center P site. Structures of TTCs containing short spacers show a state incompatible with NusG bridging and NusA binding (TTC-A, previously termed "expressome"). Structures of TTCs containing longer spacers reveal a new state compatible with NusG bridging and NusA binding (TTC-B) and reveal how NusG bridges and NusA binds. We propose that TTC-B mediates NusG- and NusA-dependent transcription-translation coupling.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cryoelectron Microscopy
  • DNA-Directed RNA Polymerases / chemistry*
  • Escherichia coli / genetics*
  • Escherichia coli Proteins / chemistry*
  • Gene Expression Regulation, Bacterial
  • Peptide Elongation Factors / chemistry*
  • Protein Binding
  • Protein Biosynthesis*
  • Protein Conformation
  • RNA, Messenger / chemistry
  • Transcription Factors / chemistry*
  • Transcription, Genetic*
  • Transcriptional Elongation Factors / chemistry*


  • Escherichia coli Proteins
  • NusG protein, E coli
  • Peptide Elongation Factors
  • RNA, Messenger
  • Transcription Factors
  • Transcriptional Elongation Factors
  • nusA protein, E coli
  • DNA-Directed RNA Polymerases