The vacuolating toxin from Helicobacter pylori forms hexameric pores in lipid bilayers at low pH

Proceedings of the National Academy of Sciences of the United States of America - Tập 96 Số 5 - Trang 2001-2006 - 1999
Daniel M. Czajkowsky1, Hideki Iwamoto1, Timothy L. Cover1, Zhifeng Shao1
1Department of Molecular Physiology and Biological Physics and Biophysics Program, University of Virginia School of Medicine, Charlottesville, VA 22908; and Departments of Medicine and Microbiology and Immunology, Vanderbilt University School of Medicine and Veterans Affairs Medical Center, Nashville, TN 37232

Tóm tắt

Pathogenic strains of Helicobacter pylori secrete a cytotoxin, VacA, that in the presence of weak bases, causes osmotic swelling of acidic intracellular compartments enriched in markers for late endosomes and lysosomes. The molecular mechanisms by which VacA causes this vacuolation remain largely unknown. At neutral pH, VacA is predominantly a water-soluble dodecamer formed by two apposing hexamers. In this report, we show by using atomic force microscopy that below pH ≈5, VacA associates with anionic lipid bilayers to form hexameric membrane-associated complexes. We propose that water-soluble dodecameric VacA proteins disassemble at low pH and reassemble into membrane-spanning hexamers. The surface contour of the membrane-bound hexamer is strikingly similar to the outer surface of the soluble dodecamer, suggesting that the VacA surface in contact with the membrane is buried within the dodecamer before protonation. In addition, electrophysiological measurements indicate that, under the conditions determined by atomic force microscopy for membrane association, VacA forms pores across planar lipid bilayers. This low pH-triggered pore formation is likely a critical step in VacA activity.

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Proceedings of the National Academy of Sciences of the United States of America

Tập 96 Số 5

2001-2006

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