Outer membrane targeting of passenger proteins by the vacuolating cytotoxin autotransporter of Helicobacter pylori

Helicobacter pylori produces a number of proteins associated with the outer membrane, including adhesins and the vacuolating cytotoxin. These proteins are supposed to integrate into the outer membrane by beta -barrel structur es, characteristic of the family of autotransporter proteins. By using the SOMPES (shuttle vector-based outer membrane protein expression) system for outer membrane protein production, we were able to functionally express in H. pylori the cholera toxin B subunit genetically fused to the C-terminal V acA domain. We demonstrate that the fusion protein is translocated to the H . pylori outer membrane and that the CtxB domain is exposed on the H. pylor i surface. Thus, we provide the first experimental evidence that the C-term inal beta -domain of VacA can transport a foreign passenger protein to the H. pylori surface and hence acts as a functional autotransporter.