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. 2002 Nov 1;367(Pt 3):617–628. doi: 10.1042/BJ20020714

Exoenzyme S shows selective ADP-ribosylation and GTPase-activating protein (GAP) activities towards small GTPases in vivo.

Maria L Henriksson 1, Charlotta Sundin 1, Anna L Jansson 1, Ake Forsberg 1, Ruth H Palmer 1, Bengt Hallberg 1
PMCID: PMC1222916  PMID: 12132999

Abstract

Intracellular targeting of the Pseudomonas aeruginosa toxins exoenzyme S (ExoS) and exoenzyme T (ExoT) initially results in disruption of the actin microfilament structure of eukaryotic cells. ExoS and ExoT are bifunctional cytotoxins, with N-terminal GTPase-activating protein (GAP) and C-terminal ADP-ribosyltransferase activities. We show that ExoS can modify multiple GTPases of the Ras superfamily in vivo. In contrast, ExoT shows no ADP-ribosylation activity towards any of the GTPases tested in vivo. We further examined ExoS targets in vivo and observed that ExoS modulates the activity of several of these small GTP-binding proteins, such as Ras, Rap1, Rap2, Ral, Rac1, RhoA and Cdc42. We suggest that ExoS is the major ADP-ribosyltransferase protein modulating small GTPase function encoded by P. aeruginosa. Furthermore, we show that the GAP activity of ExoS abrogates the activation of RhoA, Cdc42 and Rap1.

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Selected References

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