Aeromonas exoenzyme T of Aeromonas salmonicida is a bifunctional protein that targets the host cytoskeleton

Fehr, Désirée; Burr, Sarah E; Gibert, Maryse; d'Alayer, Jacques; Frey, Joachim; Popoff, Michel R (2007). Aeromonas exoenzyme T of Aeromonas salmonicida is a bifunctional protein that targets the host cytoskeleton. Journal of biological chemistry, 282(39), pp. 28843-52. Bethesda, Md.: American Society for Biochemistry and Molecular Biology 10.1074/jbc.M704797200

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Type III protein secretion has been shown recently to be important in the virulence of the fish pathogen Aeromonas salmonicida. The ADP-ribosylating toxin Aeromonas exoenzyme T (AexT) is one effector protein targeted for secretion via this system. In this study, we identified muscular and nonmuscular actin as substrates of the ADP-ribosylating activity of AexT. Furthermore, we show that AexT also functions as a GTPase-activating protein (GAP), displaying GAP activity against monomeric GTPases of the Rho family, specifically Rho, Rac, and Cdc42. Transfection of fish cells with wild type AexT resulted in depolymerization of the actin cytoskeleton and cell rounding. Point mutations within either the GAP or the ADP-ribosylating active sites of AexT (Arg-143 as well as Glu-398 and Glu-401, respectively) abolished enzymatic activity, yet did not prevent actin filament depolymerization. However, inactivation of the two catalytic sites simultaneously did. These results suggest that both the GAP and ADP-ribosylating domains of AexT contribute to its biological activity. This is the first bacterial virulence factor to be described that has a specific actin ADP-ribosylation activity and GAP activity toward Rho, Rac, and Cdc42, both enzymatic activities contributing to actin filament depolymerization.

Item Type:

Journal Article (Original Article)


05 Veterinary Medicine > Department of Infectious Diseases and Pathobiology (DIP) > Institute of Veterinary Bacteriology

UniBE Contributor:

Fehr, Désirée, Burr, Sarah Ellen, Frey, Joachim




American Society for Biochemistry and Molecular Biology




Factscience Import

Date Deposited:

04 Oct 2013 14:53

Last Modified:

05 Dec 2022 14:16

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URI: (FactScience: 34867)

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