Molecular analysis of the Vibrio cholerae type II secretion ATPase EpsE. Author Jodi Camberg, Maria Sandkvist Publication Year 2005 Type Journal Article Abstract 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. Keywords Vibrio cholerae, Bacterial Proteins, Membrane Proteins, Adenosine Triphosphate, Zinc Journal J Bacteriol Volume 187 Issue 1 Pages 249-56 Date Published 2005 Jan ISSN Number 0021-9193 DOI 10.1128/JB.187.1.249-256.2005 Alternate Journal J Bacteriol PMCID PMC538811 PMID 15601709 PubMedPubMed CentralGoogle ScholarBibTeXEndNote X3 XML