Mutation of cytotoxin-associated gene A affects expressions of antioxidant proteins of Helicobacter pylori

AIM： To determine if disruption of the cagA gene of Helicobacter pylori （H pylori） has an effect on the expression of other proteins at proteome level. METHODS： Construction of a cagA knock out mutant Hp27_△cagA （cagA） via homologous recombination with the wild-type strain Hp27 （cagA＋） as a recipient was performed. The method of sonication-urea-CHAPS-DTT was employed to extract bacterial proteins from both strains. Soluble proteins were analyzed by two-dimensional electrophoresis （2-DE）. Images of 2-DE gels were digitalized and analyzed. Only spots that had a statistical significance in differential expression were selected and analyzed by matrix-assisted laser desorption/ionization- time of flight mass spectrometry （MALDI-TOF-MS）. Biological information was used to search protein database and identify the biological function of proteins. RESULTS： The proteome expressions between wild-type strain and isogenic mutant with the cagA gene knocked-out were compared. Five protein spots with high abundance in bacteria proteins of wild-type strains, down-regulated or absently expressed in bacteria proteins of mutants, were identified and analyzed. From a quantitative point of view, the identified proteins are related to the cagA gene and important antioxidant proteins of Hpylori, including alkyl hydroperoxide reductase （Ahp）, superoxide dismutase （SOD） and modulator of drug activity （Mda66）, respectively, suggesting that cagA is important to maintain the normal activity of antioxidative stress and ensure H pylori persistent colonization in the host. CONCLUSION： cagA gene is relevant to the expressions of antioxidant proteins of H pylori, which may be a novel mechanism involved in H pylori cagA pathogenesis.