Type III machines of pathogenic yersiniae secrete virulence factors into the extracellular milieu

Mol Microbiol. 1999 Mar;31(6):1619-29. doi: 10.1046/j.1365-2958.1999.01270.x.


Gram-negative bacteria use type III machines to inject toxic proteins into the cytosol of eukaryotic cells. Pathogenic Yersinia species export 14 Yop proteins by the type III pathway and some of these, named effector Yops, are targeted into macrophages, thereby preventing phagocytosis and allowing bacterial replication within lymphoid tissues. Hitherto, YopB/YopD were thought to insert into the plasma membrane of macrophages and to promote the import of effector Yops into the eukaryotic cytosol. We show here that the type III machines of yersiniae secrete three proteins into the extracellular milieu (YopB, YopD and YopR). Although intrabacterial YopD is required for the injection of toxins into eukaryotic cells, secreted YopB, YopD and YopR are dispensable for this process. Nevertheless, YopB, YopD and YopR are essential for the establishment of Yersinia infections in a mouse model system, suggesting that type III secretion machines function to deliver virulence factors into the extracellular milieu also.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Bacterial Outer Membrane Proteins / genetics
  • Bacterial Outer Membrane Proteins / metabolism
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • Digitonin / metabolism
  • Electrophoresis, Polyacrylamide Gel
  • Endopeptidase K / metabolism
  • Female
  • Fluorescent Antibody Technique
  • HeLa Cells
  • Humans
  • Immunoblotting
  • Mice
  • Mice, Inbred BALB C
  • Mutagenesis
  • Protein Tyrosine Phosphatases / genetics
  • Protein Tyrosine Phosphatases / metabolism
  • Virulence / physiology*
  • Yersinia / pathogenicity*
  • Yersinia / physiology


  • Bacterial Outer Membrane Proteins
  • Bacterial Proteins
  • YopB protein, Yersinia
  • YopD protein, Yersinia
  • yopE protein, Yersinia
  • Protein Tyrosine Phosphatases
  • yopH protein, Yersinia
  • Endopeptidase K
  • Digitonin