Expression of Latent P-Type ATPases and Their Presumptive Roles in Cell Membrane of Helicobacter pylori

Cation motive ATPases on cell membranes of Helicobacter pylori were investigated using everted membrane vesicles. Latent ATPases could be ascertained from aggregated vesicle using N, N-dimethylformamide (DMF) and Triton X-100. By contrast, ultrasonication or chloroform treatments caused membranes to be disrupted, resulting in an alteration of sensitivities against azide or vanadate. Considerable amounts of vanadate-sensitive enzymes were identified from vesicle micelles, prepared by the dilution method. These were activated in the presence of either $Ni^{2+}\;or\;NH_4^+$. From studies employing H. pylori intact cell systems, we found that ATPase expression of this bacterium was markedly dependent upon air composition. It was interesting that cellular expression of $Ni^{2+}$- or $NH_4^{+}$-motive ATPases was significantly affected by extracellular pH, suggesting that these unique enzymes may physiologically be involved in cellular $Ni^2$ import and $NH_4^+$ export, respectively.