The N-terminal Domain of Pseudomonas aeruginosaExoenzyme S Is a GTPase-activating Protein for Rho GTPases*
- Udo-Michael Goehring‡,
- Gudula Schmidt‡§,
- Kristin J. Pederson¶‖,
- Klaus Aktoriesठand
- Joseph T. Barbieri¶**
- From the ‡Institut für Pharmakologie und Toxikologie, Albert-Ludwigs-Universität Freiburg, D-79104 Freiburg, Germany and ¶Medical College of Wisconsin, Microbiology and Molecular Genetics, Milwaukee, Wisconsin 53226
Abstract
Pseudomonas aeruginosa exoenzyme S (ExoS) is a bifunctional cytotoxin. The ADP-ribosyltransferase domain is located within the C terminus part of ExoS. Recent studies showed that the N terminus part of ExoS (amino acid residues 1–234, ExoS(1–234)), which does not possess ADP-ribosyltransferase activity, stimulates cell rounding when transfected or microinjected into eukaryotic cells. Here we studied the effects of ExoS(1–234) on nucleotide binding and hydrolysis by Rho GTPases. ExoS(1–234) (100–500 nm) did not influence nucleotide exchange of Rho, Rac, and Cdc42 but increased GTP hydrolysis. A similar increase in GTPase activity was stimulated by full-length ExoS. Half-maximal stimulation of GTP hydrolysis by Rho, Rac, and Cdc42 was observed at 10–11 nm ExoS(1–234), respectively. We identified arginine 146 of ExoS to be essential for the stimulation of GTPase activity of Rho proteins. These data identify ExoS as a GTPase-activating protein for Rho GTPases.
Footnotes
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↵* The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵§ Supported by the Deutsche Forschungsgemeinschaft.
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↵‖ Supported by National Institutes of Health Grant AI10017 (NIAID).
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↵** Supported by National Institutes of Health Grant AI30162 (NIAID). To whom correspondence should be addressed: Medical College of Wisconsin, Microbiology and Molecular Genetics, 8701 Watertown Plank Rd., Milwaukee, WI 53226. Tel.: 414-456-8412; Fax: 414-456-6535; E-mail: toxin@mcw.edu.
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↵2 G. Schmidt, U.-M. Goehring, J. Schirmer, M. Lerm, and K. Aktories, submitted for publication.
- Abbreviations:
- CNF
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cytotoxic necrotizing factor
- GAP
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GTPase-activating protein
- ExoS
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exoenzyme S
- GST
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glutathione S-transferase
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- Received August 16, 1999.
- Revision received September 27, 1999.
- The American Society for Biochemistry and Molecular Biology, Inc.
