In-cell architecture of an actively transcribing-translating expressome

Science. 2020 Jul 31;369(6503):554-557. doi: 10.1126/science.abb3758.


Structural biology studies performed inside cells can capture molecular machines in action within their native context. In this work, we developed an integrative in-cell structural approach using the genome-reduced human pathogen Mycoplasma pneumoniae We combined whole-cell cross-linking mass spectrometry, cellular cryo-electron tomography, and integrative modeling to determine an in-cell architecture of a transcribing and translating expressome at subnanometer resolution. The expressome comprises RNA polymerase (RNAP), the ribosome, and the transcription elongation factors NusG and NusA. We pinpointed NusA at the interface between a NusG-bound elongating RNAP and the ribosome and propose that it can mediate transcription-translation coupling. Translation inhibition dissociated the expressome, whereas transcription inhibition stalled and rearranged it. Thus, the active expressome architecture requires both translation and transcription elongation within the cell.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / metabolism
  • DNA-Directed RNA Polymerases / metabolism
  • Genome, Bacterial
  • Humans
  • Mycoplasma pneumoniae / genetics
  • Mycoplasma pneumoniae / metabolism*
  • Mycoplasma pneumoniae / ultrastructure*
  • Peptide Chain Elongation, Translational*
  • Peptide Elongation Factors / metabolism
  • Protein Interaction Maps*
  • Ribosomes / metabolism
  • Transcription, Genetic*
  • Transcriptome


  • Bacterial Proteins
  • Peptide Elongation Factors
  • DNA-Directed RNA Polymerases