Genetic microheterogeneity and phenotypic variation of Helicobacter pylori arginase in clinical isolates.
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.


CONCLUSIONS
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.
Hovey
Justin G
JG
Department of Microbiology and Immunology, University of South Alabama College of Medicine, Mobile, AL, USA. justinhovey@gmail.com <justinhovey@gmail.com>
Watson
Emily L
EL
Langford
Melanie L
ML
Hildebrandt
Ellen
E
Bathala
Sangeetha
S
Bolland
Jeffrey R
JR
Spadafora
Domenico
D
Mendz
George L
GL
McGee
David J
DJ
D001119:Arginase / Q000235:genetics* / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D015153:Blotting, Western; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004591:Electrophoresis, Polyacrylamide Gel; D015964:Gene Expression Regulation, Bacterial; D018740:Genetic Heterogeneity; D014644:Genetic Variation; D016481:Helicobacter Infections / Q000382:microbiology; D016480:Helicobacter pylori / Q000201:enzymology / Q000235:genetics*; D006801:Humans; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010641:Phenotype; D010802:Phylogeny; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D012694:Serine / Q000235:genetics / Q000378:metabolism; D014510:Urease / Q000378:metabolism
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D012694:Serine; D014510:Urease; C402431:RocF protein, Helicobacter pylori; D001119:Arginase