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Journal of Bacteriology, January 2005, p. 249-256, Vol. 187, No. 1
0021-9193/05/$08.00+0     doi:10.1128/JB.187.1.249-256.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

Molecular Analysis of the Vibrio cholerae Type II Secretion ATPase EpsE

Jodi L. Camberg and Maria Sandkvist*

Department of Medicine, Division of Infectious Diseases, University of Maryland School of Medicine, Rockville, Maryland

Received 19 May 2004/ Accepted 20 September 2004

The type II secretion system is a macromolecular assembly that facilitates the extracellular translocation of folded proteins in gram-negative bacteria. EpsE, a member of this secretion system in Vibrio cholerae, contains a nucleotide-binding motif composed of Walker A and B boxes that are thought to participate in binding and hydrolysis of ATP and displays structural homology to other transport ATPases. Here we demonstrate that purified EpsE is an Mg2+-dependent ATPase and define optimal conditions for the hydrolysis reaction. EpsE displays concentration-dependent activity, which may suggest that the active form is oligomeric. Size exclusion chromatography showed that the majority of purified EpsE is monomeric; however, detailed analyses of specific activities obtained following gel filtration revealed the presence of a small population of active oligomers. We further report that EpsE binds zinc through a tetracysteine motif near its carboxyl terminus, yet metal displacement assays suggest that zinc is not required for catalysis. Previous studies describing interactions between EpsE and other components of the type II secretion pathway together with these data further support the hypothesis that EpsE functions to couple energy to the type II apparatus, thus enabling secretion.

* Corresponding author. Mailing address: Department of Medicine, Division of Infectious Diseases, University of Maryland School of Medicine, 15601 Crabbs Branch Way, Rockville, MD 20855. Phone: (301) 738-0604. Fax: (301) 738-0740. E-mail: Sandkvis{at}usa.redcross.org.

Journal of Bacteriology, January 2005, p. 249-256, Vol. 187, No. 1
0021-9193/05/$08.00+0     doi:10.1128/JB.187.1.249-256.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.



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