Contribution of dppA to urease activity in Helicobacter pylori 26695.
BACKGROUND
The gastric pathogen Helicobacter pylori produces urease in amounts up to 10% of its cell protein. This enzyme, which catalyzes the hydrolysis of urea to ammonia and carbon dioxide, protects the bacterium from gastric acid. Urease, a nickel metalloenzyme, requires active uptake of nickel ions from the environment to maintain its activity. NixA is a nickel transport protein that resides in the cytoplasmic membrane. Mutation of nixA significantly reduces but does not abolish urease activity, strongly suggesting the presence of a second transporter. We postulated that the dipeptide permease (dpp) genes that are homologous to the nik operon of Escherichia coli could be a second nickel transporter. The predicted Dpp polypeptides DppA, DppC, and DppD of H. pylori share approximately 40%, 53%, and 56% amino acid sequence identity with their respective E. coli homologs.


METHODS
A mutation in dppA, constructed by insertional inactivation with a chloramphenicol resistance cassette, was introduced by allelic exchange into H. pylori strain 26695.


RESULTS
When compared to the parental strain, urease activity was not decreased in a dppA mutant.


CONCLUSIONS
DppA does not contribute to the synthesis of catalytically active urease in H. pylori 26695 and is likely not a nickel importer in H. pylori.
Davis
Gregg S
GS
Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor 48109-0620, USA.
Mobley
Harry L T
HL
D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D016480:Helicobacter pylori / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D006801:Humans; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D008826:Microbial Sensitivity Tests; D009154:Mutation; D009532:Nickel / Q000378:metabolism / Q000494:pharmacology; D009876:Operon; D014510:Urease / Q000378:metabolism*
D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins; D026901:Membrane Transport Proteins; C037230:oligopeptide permease, Bacteria; D009532:Nickel; D014510:Urease