Helicobacter pylori VacA Toxin/Subunit p34: Targeting of an Anion Channel to the Inner Mitochondrial Membrane
| Autor: | Elke A. Dian-Lothrop, Joachim Rassow, Antoine Galmiche, Oliver Kepp, Kathrin Günnewig, Grazyna Domanska, Anke Harsman, Christian Motz, Richard Wagner, Lars Becker, Michael Meinecke, Boris Reljic, Panagiotis Papatheodorou |
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| Rok vydání: | 2010 |
| Předmět: |
QH301-705.5
Protein subunit Immunology TIM/TOM complex Mitochondrion Biology Microbiology Mitochondrial apoptosis-induced channel Cell Biology/Membranes and Sorting Bacterial Proteins Virology Genetics Animals Humans Biology (General) Inner mitochondrial membrane Molecular Biology Helicobacter pylori RC581-607 Rats Electrophysiology Microscopy Fluorescence Membrane protein Biochemistry Biophysics/Membrane Proteins and Energy Transduction Mitochondrial Membranes Translocase of the inner membrane Parasitology Immunologic diseases. Allergy Microbiology/Cellular Microbiology and Pathogenesis Bacterial outer membrane Research Article HeLa Cells |
| Zdroj: | PLoS Pathogens PLoS Pathogens, Vol 6, Iss 4, p e1000878 (2010) Scopus-Elsevier |
| ISSN: | 1553-7374 |
| DOI: | 10.1371/journal.ppat.1000878 |
| Popis: | 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% β-strands, similar to pore-forming β-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. Author Summary VacA is a toxic protein produced by Helicobacter pylori, the bacteria that cause gastritis and ulcer diseases. p34, the toxic component of VacA, is known to damage mitochondria, defined cell organelles in the target cells. However, both the mechanism of mitochondrial targeting and the toxic activity inside the mitochondria are unclear. In this study, we show that p34 carries a unique targeting signal that is different from all targeting signatures that were previously identified in endogenous mitochondrial proteins. Eventually, p34 seems to act as an anion channel in the mitochondrial inner membrane and thus to destroy the balance of salt ions in the organelles. |
| Databáze: | OpenAIRE |
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