VacA from Helicobacter pylori: a hexameric chloride channel

FEBS Letters

Czajkowsky, Daniel M.¹  Szabo, Gabor¹  Shao, Zhifeng¹  Iwamoto, Hideki¹  Cover, Timothy L.² 

[1] Department of Molecular Physiology and Biological Physics and Biophysics Program, University of Virginia School of Medicine, Charlottesville, VA 22908, USA;Departments of Medicine and Microbiology and Immunology, Vanderbilt University School of Medicine and VA Medical Center, Nashville, TN 37232, USA

关键词: Ulcer;    Vacuolating toxin;    Anion selective;    Atomic force microscopy;    VacA;    vacuolating toxin;    DIDS;    4;    4′-diisothiocyanatostilbene-2;    2′-disulfonic acid;    eggPC;    egg phosphatidylcholine;    DOPS;    dioleoylphosphatidylserine;    HL;    total lipid extract from bovine heart;    AFM;    atomic force microscopy;   

DOI  :  10.1016/S0014-5793(99)00474-3

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

VacA is a unique protein toxin secreted by the human pathogen Helicobacter pylori. At a neutral pH, the cytotoxin self-associates into predominantly dodecameric complexes. In this report, we show that at an acidic pH, VacA forms anion selective channels in planar phospholipid bilayers. Similar to several other chloride channels, the VacA channel exhibits a moderate selectivity for anions over cations (P_Cl:P_Na=4.2:1), inhibition by the blocker 4,4′-diisothiocyanatostilbene-2,2′-disulfonic acid and a permeability sequence, SCN⁻≫I⁻>Br⁻>Cl⁻>F, consistent with a ‘weak field strength’ binding site for the permeant anion. Single channel recordings reveal rapid transitions (486 s⁻¹) between the closed state and a single open state of 24 pS (+60 mV, 1.5 M NaCl). Evaluation of the rate of increase in macroscopic current as well as atomic force microscopy suggest that this VacA channel is a hexamer, formed by the assembly of membrane-bound monomers. Not only are these VacA channels likely to play an important role in the pathological activity of this toxin, but they may also serve as a model system to further investigate the mechanism of anion selectivity in general.

【 授权许可】

Unknown