Three-dimensional model of Salmonella's needle complex at subnanometer resolution

Science. 2011 Mar 4;331(6021):1192-5. doi: 10.1126/science.1199358.


Type III secretion systems (T3SSs) are essential virulence factors used by many Gram-negative bacteria to inject proteins that make eukaryotic host cells accessible to invasion. The T3SS core structure, the needle complex (NC), is a ~3.5 megadalton-sized, oligomeric, membrane-embedded complex. Analyzing cryo-electron microscopy images of top views of NCs or NC substructures from Salmonella typhimurium revealed a 24-fold symmetry for the inner rings and a 15-fold symmetry for the outer rings, giving an overall C3 symmetry. Local refinement and averaging showed the organization of the central core and allowed us to reconstruct a subnanometer composite structure of the NC, which together with confident docking of atomic structures reveal insights into its overall organization and structural requirements during assembly.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / chemistry*
  • Bacterial Proteins / ultrastructure
  • Bacterial Secretion Systems*
  • Cryoelectron Microscopy
  • Crystallography, X-Ray
  • Image Processing, Computer-Assisted
  • Membrane Proteins / chemistry*
  • Membrane Proteins / ultrastructure
  • Membrane Transport Proteins / chemistry*
  • Membrane Transport Proteins / ultrastructure
  • Models, Molecular
  • Mutation
  • Protein Conformation
  • Protein Structure, Tertiary
  • Salmonella typhimurium / chemistry*


  • Bacterial Proteins
  • Bacterial Secretion Systems
  • Membrane Proteins
  • Membrane Transport Proteins
  • PrgH protein, Salmonella typhimurium
  • PrgK protein, Salmonella typhimurium
  • invG protein, Salmonella typhimurium

Associated data

  • PDB/2Y9J
  • PDB/2Y9K