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Characterization of Pseudomonas aeruginosa exoenzyme S as a bifunctional enzyme in J774A.1 macrophages. Infect Immun 2003 Sep;71(9):5296-305 PMID: 12933877 PMCID: PMC187317

Pubmed ID



Pseudomonas aeruginosa exoenzyme S (ExoS) is a type III secretion (TTS) effector, which includes both a GTPase-activating protein (GAP) activity toward the Rho family of low-molecular-weight G (LMWG) proteins and an ADP-ribosyltransferase (ADPRT) activity that targets LMWG proteins in the Ras, Rab, and Rho families. The coordinate function of both activities of ExoS in J774A.1 macrophages was assessed by using P. aeruginosa strains expressing and translocating wild-type ExoS or ExoS defective in GAP and/or ADPRT activity. Distinct and coordinated functions were identified for both domains. The GAP activity was required for the antiphagocytic effect of ExoS and was linked to interference of lamellopodium and membrane ruffle formation. Alternatively, the ADPRT activity of ExoS altered cellular adherence and morphology and was linked to effects on filopodium formation. The cellular mechanism of ExoS GAP activity included an inactivation of Rac1 function, as determined in p21-activated kinase 1-glutathione S-transferase (GST) pull-down assays. The ADPRT activity of ExoS targeted Ras and RalA but not Rab or Rho proteins, and Ral binding protein 1-GST pull-down assays identified an effect of ExoS ADPRT activity on RalA activation. The results from these studies confirm the bifunctional nature of ExoS activity within macrophages when translocated by TTS.

Author List

Rocha CL, Coburn J, Rucks EA, Olson JC


Jenifer Coburn PhD Professor in the Medicine department at Medical College of Wisconsin


2-s2.0-0041322625   36 Citations

MESH terms used to index this publication - Major topics in bold

ADP Ribose Transferases
Bacterial Toxins
Biological Transport, Active
Cell Line
GTP Phosphohydrolases
GTPase-Activating Proteins
Microscopy, Electron, Scanning
Pseudomonas aeruginosa
rac1 GTP-Binding Protein
ral GTP-Binding Proteins
jenkins-FCD Prod-300 626508253d14e4184314fb9f66322a03a5906796