Activation of Helicobacter pylori VacA toxin by alkaline or acid conditions increases its binding to a 250-kDa receptor protein-tyrosine phosphatase beta

Helicobacter pylori, a Gram-negative gastric bacterium, secretes VacA, a cy totoxin that causes vacuolar degeneration of susceptible cells. Velocity se dimentation analysis showed that treatment of VacA at alkaline pH led to di sassembly of VacA oligomers, an observation reported previously for acid-tr eated VacA, Exposure of VacA to acid or alkali increased its binding to AZ- 521 cells, as shown by indirect immunofluorescence and flow cytometry, More over, immunoprecipitates with polyclonal antibodies against VacA from AZ-52 1 cells previously exposed to acid- or alkali-treated VacA had a 250-kDa gl ycoprotein containing galactose-beta(1-3)-N-acetylgalactosamine and galacto se-beta(1-4)-N-acetylglucosamine, p250, purified by chromatography on peanu t agglutinin affinity and Superose 6 columns, contained N-terminal and inte rnal amino acid sequences of YRQQRKLVEEIGWSYT and LIIQDHILEATQDDY, respecti vely. These sequences are identical to those of a receptor protein-tyrosine phosphatase (RPTP beta/PTP zeta); in agreement, p250 reacted with anti-hum an RPTP beta monoclonal antibody. Immunoprecipitation with antihuman RPTP b eta antibody of solubilized membrane preparations previously incubated with VacA or heat-inactivated VacA demonstrated that RPTP beta bound native, bu t not denatured, VacA. Acidic and alkaline treatments were associated with activation of VacA and increased binding to the cell surface RPTP beta.