Cryo-EM structure of the bacteria-killing type IV secretion system core complex from Xanthomonas citri

Nat Microbiol. 2018 Dec;3(12):1429-1440. doi: 10.1038/s41564-018-0262-z. Epub 2018 Oct 22.


Type IV secretion (T4S) systems form the most common and versatile class of secretion systems in bacteria, capable of injecting both proteins and DNAs into host cells. T4S systems are typically composed of 12 components that form 2 major assemblies: the inner membrane complex embedded in the inner membrane and the core complex embedded in both the inner and outer membranes. Here we present the 3.3 Å-resolution cryo-electron microscopy model of the T4S system core complex from Xanthomonas citri, a phytopathogen that utilizes this system to kill bacterial competitors. An extensive mutational investigation was performed to probe the vast network of protein-protein interactions in this 1.13-MDa assembly. This structure expands our knowledge of the molecular details of T4S system organization, assembly and evolution.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacteria / metabolism*
  • Bacterial Outer Membrane Proteins / chemistry
  • Bacterial Outer Membrane Proteins / genetics
  • Bacterial Proteins / chemistry*
  • Bacterial Proteins / genetics
  • Cloning, Molecular
  • Cryoelectron Microscopy / methods*
  • Gene Expression Regulation, Bacterial
  • Models, Molecular
  • Multiprotein Complexes / chemistry*
  • Multiprotein Complexes / genetics
  • Mutation
  • Protein Binding
  • Protein Conformation
  • Protein Conformation, alpha-Helical
  • Protein Interaction Domains and Motifs
  • Type IV Secretion Systems / chemistry*
  • Type IV Secretion Systems / genetics
  • Xanthomonas / genetics
  • Xanthomonas / metabolism*


  • Bacterial Outer Membrane Proteins
  • Bacterial Proteins
  • Multiprotein Complexes
  • Type IV Secretion Systems