Structure of the Yersinia injectisome in intracellular host cell phagosomes revealed by cryo FIB electron tomography

Casper Berger, Raimond B. G. Ravelli, Carmen Lopez-Iglesias, Mikhail Kudryashev, Andreas Diepold, Peter J. Peters*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review


Many pathogenic bacteria use the type III secretion system (T3SS), or injectisome, to secrete toxins into host cells. These protruding systems are primary targets for drug and vaccine development. Upon contact between injectisomes and host membranes, toxin secretion is triggered. How this works structurally and functionally is yet unknown. Using cryo-focused ion beam milling and cryo-electron tomography, we visualized injectisomes of Yersinia enterocolitica inside the phagosomes of infected human myeloid cells in a close-to-native state. We observed that a minimum needle length is required for injectisomes to contact the host membrane and bending of host membranes by some injectisomes that contact the host. Through subtomogram averaging, the structure of the entire injectisome was determined, which revealed structural differences in the cytosolic sorting platform compared to other bacteria. These findings contribute to understanding how injectisomes secrete toxins into host cells and provides the indispensable native context. The application of these cryo-electron microscopy techniques paves the way for the study of the 3D structure of infection-relevant protein complexes in host-pathogen interactions.

Original languageEnglish
Article number107701
Number of pages11
JournalJournal of Structural Biology
Issue number1
Publication statusPublished - Mar 2021


  • Type III secretion system
  • Cryo-electron tomography
  • Cryo-focused ion beam lamella
  • Subtomogram averaging
  • Yersinia enterocolitica
  • Bacterial adhesin YadA

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