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Infection and Immunity, March 2006, p. 1786-1794, Vol. 74, No. 3
0019-9567/06/$08.00+0     doi:10.1128/IAI.74.3.1786-1794.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

A Helicobacter pylori Vacuolating Toxin Mutant That Fails To Oligomerize Has a Dominant Negative Phenotype

Christophe Genisset,1,2 Cesira L. Galeotti,1 Pietro Lupetti,3 David Mercati,3 David A. G. Skibinski,1 Silvia Barone,1 Roberto Battistutta,2,4 Marina de Bernard,2,5 and John L. Telford1*

IRIS, Chiron Srl, Via Fiorentina 1, 53100 Siena, Italy,1 Venetian Institute of Molecular Medicine, Via Orus 2, 35129 Padova, Italy,2 Department of Evolutionary Biology, University of Siena, Via Aldo Moro 2, 53100 Siena, Italy,3 Dipartimento di Scienze Chimiche, Università di Padova, via Marzolo 1, 35131 Padova, Italy,4 Dipartimento di Biologia, Università di Padova, Via G. Colombo 3, 35121 Padova, Italy5

Received 11 November 2005/ Returned for modification 5 December 2005/ Accepted 23 December 2005

Most Helicobacter pylori strains secrete a toxin (VacA) that causes massive vacuolization of target cells and which is a major virulence factor of H. pylori. The VacA amino-terminal region is required for the induction of vacuolization. The aim of the present study was a deeper understanding of the critical role of the N-terminal regions that are protected from proteolysis when VacA interacts with artificial membranes. Using a counterselection system, we constructed an H. pylori strain, SPM 326-{Delta}49-57, that produces a mutant toxin with a deletion of eight amino acids in one of these protected regions. VacA {Delta}49-57 was correctly secreted by H. pylori but failed to oligomerize and did not have any detectable vacuolating cytotoxic activity. However, the mutant toxin was internalized normally and stained the perinuclear region of HeLa cells. Moreover, the mutant toxin exhibited a dominant negative effect, completely inhibiting the vacuolating activity of wild-type VacA. This loss of activity was correlated with the disappearance of oligomers in electron microscopy. These findings indicate that the deletion in VacA {Delta}49-57 disrupts the intermolecular interactions required for the oligomerization of the toxin.

* Corresponding author. Mailing address: IRIS, Chiron Srl, Via Fiorentina, 1, 53100 Siena, Italy. Phone: 390577243470. Fax: 390577243564. E-mail: john_telford{at}chiron.com.

Editor: J. T. Barbieri

Infection and Immunity, March 2006, p. 1786-1794, Vol. 74, No. 3
0019-9567/06/$08.00+0     doi:10.1128/IAI.74.3.1786-1794.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

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