title: Helicobacter pylori VacA toxin/subunit p34: targeting of an anion channel to the inner mitochondrial membrane.
abstract: The vacuolating toxin VacA, released by Helicobacter pylori, is an important virulence factor in the pathogenesis of gastritis and gastroduodenal ulcers. VacA contains two subunits: The p58 subunit mediates entry into target cells, and the p34 subunit mediates targeting to mitochondria and is essential for toxicity. In this study we found that targeting to mitochondria is dependent on a unique signal sequence of 32 uncharged amino acid residues at the p34 N-terminus. Mitochondrial import of p34 is mediated by the import receptor Tom20 and the import channel of the outer membrane TOM complex, leading to insertion of p34 into the mitochondrial inner membrane. p34 assembles in homo-hexamers of extraordinary high stability. CD spectra of the purified protein indicate a content of >40% beta-strands, similar to pore-forming beta-barrel proteins. p34 forms an anion channel with a conductivity of about 12 pS in 1.5 M KCl buffer. Oligomerization and channel formation are independent both of the 32 uncharged N-terminal residues and of the p58 subunit of the toxin. The conductivity is efficiently blocked by 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB), a reagent known to inhibit VacA-mediated apoptosis. We conclude that p34 essentially acts as a small pore-forming toxin, targeted to the mitochondrial inner membrane by a special hydrophobic N-terminal signal.
authors.affiliation: Institut für Physiologische Chemie, Ruhr-Universität Bochum, Bochum, Germany.
authors.forename: Grazyna
authors.initials: G
authors.lastname: Domańska
authors.forename: Christian
authors.initials: C
authors.lastname: Motz
authors.forename: Michael
authors.initials: M
authors.lastname: Meinecke
authors.forename: Anke
authors.initials: A
authors.lastname: Harsman
authors.forename: Panagiotis
authors.initials: P
authors.lastname: Papatheodorou
authors.forename: Boris
authors.initials: B
authors.lastname: Reljic
authors.forename: Elke A
authors.initials: EA
authors.lastname: Dian-Lothrop
authors.forename: Antoine
authors.initials: A
authors.lastname: Galmiche
authors.forename: Oliver
authors.initials: O
authors.lastname: Kepp
authors.forename: Lars
authors.initials: L
authors.lastname: Becker
authors.forename: Kathrin
authors.initials: K
authors.lastname: Günnewig
authors.forename: Richard
authors.initials: R
authors.lastname: Wagner
authors.forename: Joachim
authors.initials: J
authors.lastname: Rassow
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D004594:Electrophysiology; D006367:HeLa Cells; D016480:Helicobacter pylori / Q000378:metabolism; D006801:Humans; D008856:Microscopy, Fluorescence; D051336:Mitochondrial Membranes / Q000378:metabolism*; D051381:Rats
chemical_list: D001426:Bacterial Proteins; C074689:VacA protein, Helicobacter pylori