Figure 3.

Susceptibility of VacA proteins to proteolytic cleavage by trypsin. A) Intact H. pylori strains [wild-type strain 60190, strains expressing mutant forms of VacA, and a vacA null mutant strain (VM018)] were suspended in PBS and incubated in the presence (+) or absence (-) of trypsin as described in Methods. After centrifugation, bacterial pellets were analyzed by immunoblot analysis using polyclonal anti-VacA serum #958. (B) H. pylori strains were sonicated as described in Methods. After centrifugation, the soluble fractions were analyzed further. The total protein concentration of each sample was approximately 7.5 μg/ml, as determined by A₂₈₀ values (data not shown). Samples were incubated in the presence (+) or absence (-) of trypsin and analyzed by immunoblot analysis using polyclonal anti-VacA serum #958.