Organization and coordinated assembly of the type III secretion export apparatus

Proc Natl Acad Sci U S A. 2010 Oct 12;107(41):17745-50. doi: 10.1073/pnas.1008053107. Epub 2010 Sep 27.

Abstract

Type III protein secretion systems are unique bacterial nanomachines with the capacity to deliver bacterial effector proteins into eukaryotic cells. These systems are critical to the biology of many pathogenic or symbiotic bacteria for insects, plants, animals, and humans. Essential components of these systems are multiprotein envelope-associated organelles known as the needle complex and a group of membrane proteins that compose the so-called export apparatus. Here, we show that components of the export apparatus associate intimately with the needle complex, forming a structure that can be visualized by cryo-electron microscopy. We also show that formation of the needle complex base is initiated at the export apparatus and that, in the absence of export apparatus components, there is a significant reduction in the levels of needle complex base assembly. Our results show a substantial coordination in the assembly of the two central elements of type III secretion machines.

Publication types

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

MeSH terms

  • Bacterial Proteins / metabolism*
  • Blotting, Western
  • Cryoelectron Microscopy
  • Image Processing, Computer-Assisted
  • Immunoprecipitation
  • Membrane Transport Proteins / metabolism*
  • Multiprotein Complexes / metabolism*
  • Multiprotein Complexes / ultrastructure
  • Salmonella typhimurium / metabolism
  • Salmonella typhimurium / physiology*
  • Salmonella typhimurium / ultrastructure
  • Secretory Pathway / physiology*

Substances

  • Bacterial Proteins
  • Membrane Transport Proteins
  • Multiprotein Complexes
  • PrgH protein, Salmonella typhimurium
  • invG protein, Salmonella typhimurium