Aerolysin,a hemolysin fromAeromonas hydrophila,forms voltage-gated channels in planar lipid bilayers |
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Authors: | H U Wilmsen F Pattus J T Buckley |
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Institution: | (1) European Molecular Biology Laboratory, 6900 Heidelberg, Germany;(2) Department of Biochemistry and Microbiology, University of Victoria, V8W 2Y2 Victoria, British Columbia, Canada |
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Abstract: | Summary The cytolytic toxin aerolysin was found to form ion channels which displayed slight anion selectivity in planar lipid bilayers. In voltage-clamp experiments the ion current flowing through the channels was homogeneous indicating a defined conformation and a uniform size. The channels remained open between –70 to +70 mV, but outside this range they underwent voltage-dependent inactivation which was observed as open-closed fluctuations at the single-channel level. Zinc ions not only prevented the formation of channels by inhibiting oligomerization of monomeric aerolysin but they also induced a closure of preformed channels in a voltage-dependent fashion. The results of a Hill plot indicated that 2–3 zinc ions bound to a site within the channel lumen. Proaerolysin, and a mutant of aerolysin in which histidine 132 was replaced by an asparagine, were both unable to oligomerize and neither could form channels. This is evidence that oligomerization is a necessary step in channel formation. |
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Keywords: | Aeromonas hydrophila aerolysin ionic channel zinc ions voltage dependence planar lipid membranes |
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