The cytolethal distending toxin B sub-unit of Helicobacter hepaticus is a Ca²⁺- and Mg²⁺-dependent neutral nuclease

Authors

Rohana P. Dassanayake, University of Nebraska - Lincoln
Mark A. Griep, University of Nebraska-LincolnFollow
Gerald Duhamel, University of Nebraska - LincolnFollow

Date of this Version

October 2005

Comments

Published in FEMS Microbiology Letters 251:2 (October 2005), pp. 219–225. Copyright © 2005 Federation of European Microbiological Societies. Published by Elsevier B.V. Used by permission. http://www.sciencedirect.com/science/journal/03781097

Abstract

The cytolethal distending toxin B (CdtB) of the mouse pathogen Helicobacter hepaticus has cation binding and DNA catalysis residues in common with members of the mammalian deoxyribonuclease I (DNase I) family. The purpose of the present study was to characterize CdtB nuclease. To establish optimal digestion conditions and to evaluate co-factor requirements, a novel and sensitive fl uorometric assay that quantitatively determines double stranded DNA digestion was developed. Although the Ca²⁺- and Mg²⁺-dependence and neutral properties of CdtB were similar to DNase I, hydrolysis of DNA by CdtB was approximately 100-fold less active than DNase I and was considerably more resistant to inhibition by ZnCl₂ and G-actin.