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The human gastric pathogen Helicobacter pylori has a gene encoding an enzyme first classified as a mucinase in Vibrio
A W Smith1, B Chahal, G L French
1Department of Microbiology, UMDS Guy's Hospital Medical School, London, UK.
Abstract:
The human bacterial pathogen Helicobacter pylori has been suggested to be the causative agent of the most common chronic infection of man. Since its first isolation in 1982, H. pylori has been associated with gastric and duodenal ulcer disease, and more recently, gastric cancer. The proteolytic digestion of gastric mucus by this microorganism has been suggested as an important mechanism by which its pathogenicity is at least partly exerted. Here we report the detection of protease activity in H. pylori total-cell and supernatant extracts. On the basis that zinc metalloproteases are common microbial pathogenicity factors, we identified a single protein in H. pylori protein extracts with antibodies to the Pseudomonas aeruginosa elastase (a secreted zinc metalloprotease). This same protein was identified by pooled serum from patients infected with H. pylori. We used the functional and immunological relationship between the P. aeruginosa elastase and the Vibrio cholerae haemagglutinin/protease (HAP) to clone the H. pylori hap gene, which was over 99% similar to the V. cholerae hap gene in the coding region. A 4 kb DNA fragment containing the entire cloned gene was highly unstable in Escherichia coli and Bacillus subtilis cloning vectors. We also demonstrated that a hap-like gene sequence is present in all nine Helicobacter species so far discovered. The V. cholerae HAP was first classified on the basis of its mucinase activity.
Insights
Helicobacter pylori possesses protease activity, crucial for its pathogenicity. Researchers identified and cloned the H. pylori mucinase gene, finding it present in all Helicobacter species, suggesting a conserved virulence factor.
Area of Science:
- Microbiology
- Pathogen Research
- Molecular Biology
Background:
- Helicobacter pylori is a human pathogen linked to ulcers and gastric cancer.
- Proteolytic digestion of gastric mucus by H. pylori is a proposed pathogenicity mechanism.
- The bacterium was first isolated in 1982.
Purpose of the Study:
- To detect and characterize protease activity in H. pylori.
- To identify the specific protein responsible for this activity.
- To clone the gene encoding this protease and investigate its presence in other Helicobacter species.
Main Methods:
- Detection of protease activity in bacterial extracts.
- Immunological identification using antibodies against Pseudomonas aeruginosa elastase and patient sera.
- Gene cloning based on functional and immunological similarities to Vibrio cholerae haemagglutinin/protease (HAP).
- DNA sequencing and analysis of gene presence across Helicobacter species.
Main Results:
- Protease activity was detected in H. pylori extracts.
- A single protein, immunologically related to P. aeruginosa elastase, was identified.
- The H. pylori mucinase gene (hap) was cloned and found to be over 99% similar to V. cholerae HAP.
- A hap-like gene sequence is present in all nine currently discovered Helicobacter species.
- The cloned gene fragment was unstable in common bacterial vectors.
Conclusions:
- H. pylori possesses a zinc metalloprotease with mucinase activity, contributing to its pathogenicity.
- This protease and its gene are conserved across the Helicobacter genus.
- The identified H. pylori mucinase is functionally and immunologically related to known microbial proteases.