Control of type III secretion activity and substrate specificity by the cytoplasmic regulator PcrG

Proc Natl Acad Sci U S A. 2014 May 13;111(19):E2027-36. doi: 10.1073/pnas.1402658111. Epub 2014 Apr 28.


Pathogenic Gram-negative bacteria use syringe-like type III secretion systems (T3SS) to inject effector proteins directly into targeted host cells. Effector secretion is triggered by host cell contact, and before contact is prevented by a set of conserved regulators. How these regulators interface with the T3SS apparatus to control secretion is unclear. We present evidence that the proton motive force (pmf) drives T3SS secretion in Pseudomonas aeruginosa, and that the cytoplasmic regulator PcrG interacts with distinct components of the T3SS apparatus to control two important aspects of effector secretion: (i) It coassembles with a second regulator (Pcr1) on the inner membrane T3SS component PcrD to prevent effectors from accessing the T3SS, and (ii) In conjunction with PscO, it controls protein secretion activity by modulating the ability of T3SS to convert pmf.

Publication types

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

MeSH terms

  • Amino Acid Sequence
  • Bacterial Proteins / chemistry
  • Bacterial Proteins / genetics*
  • Bacterial Proteins / metabolism*
  • Bacterial Secretion Systems / physiology*
  • Cytoplasm / metabolism
  • Gene Expression Regulation, Bacterial
  • Molecular Sequence Data
  • Phenotype
  • Protein Structure, Tertiary
  • Proton-Motive Force / physiology
  • Pseudomonas aeruginosa / genetics*
  • Pseudomonas aeruginosa / metabolism*
  • Substrate Specificity


  • Bacterial Proteins
  • Bacterial Secretion Systems