Genetic Microheterogeneity and Phenotypic Variation of Helicobacter pylori Arginase in Clinical Isolates

Authors

Justin Hovey, University of South Alabama College of Medicine, Mobile, AL, USA
Emily Watson, Creighton University School of Medicine, Omaha, NE, USA
Melanie Langford, University of Nebraska - Lincoln
Ellen Hildebrandt, Louisiana State University Health Sciences Center, Shreveport, LA, USA
Sangeetha Bathala, University of South Alabama College of Medicine, Mobile, AL, USA
Jeffrey Bolland, University of Alabama at Birmingham, Birmingham, AL, USA
Domenico Spadafora, University of South Alabama College of Medicine, Mobile, AL, USA
George Mendz, University of New South Wales, Sydney, Australia
David McGee, Louisiana State University Health Sciences Center, Shreveport, LA, USA

Date of this Version

2007

Comments

Published in BMC Microbiology 2007, 7:26 doi:10.1186/1471-2180-7-26 This article is available from: http://www.biomedcentral.com/1471-2180/7/26 Copyright © 2007 Hovey et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Background: Clinical isolates of the gastric pathogen Helicobacter pylori display a high level of genetic macro- and microheterogeneity, featuring a panmictic, rather than clonal structure. The ability of H. pylori to survive the stomach acid is due, in part, to the arginase-urease enzyme system. Arginase (RocF) hydrolyzes L-arginine to L-ornithine and urea, and urease hydrolyzes urea to carbon dioxide and ammonium, which can neutralize acid.
Results: The degree of variation in arginase was explored at the DNA sequence, enzyme activity and protein expression levels. To this end, arginase activity was measured from 73 minimally-passaged clinical isolates and six laboratory-adapted strains of H. pylori. The rocF gene from 21 of the strains was cloned into genetically stable E. coli and the enzyme activities measured. Arginase activity was found to substantially vary (>100-fold) in both different H. pylori strains and in the E. coli model. Western blot analysis revealed a positive correlation between activity and amount of protein expressed in most H. pylori strains. Several H. pylori strains featured altered arginase activity upon in vitro passage. Pairwise alignments of the 21 rocF genes plus strain J99 revealed extensive microheterogeneity in the promoter region and 3' end of the rocF coding region. Amino acid S232, which was I232 in the arginase-negative clinical strain A2, was critical for arginase activity.
Conclusion: These studies demonstrated that H. pylori arginase exhibits extensive genotypic and phenotypic variation which may be used to understand mechanisms of microheterogeneity in H. pylori.