Aerolysin, a hemolysin from Aeromonas hydrophila, forms voltage-gated channels in planar lipid bilayers.
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.
European Molecular Biology Laboratory, Heidelberg, Federal Republic of Germany.
H U
HU
Wilmsen
F
F
Pattus
J T
JT
Buckley
D000333:Aeromonas / Q000378:metabolism*; D001427:Bacterial Toxins / Q000235:genetics / Q000378:metabolism*; D004558:Electric Stimulation; D006460:Hemolysin Proteins / Q000235:genetics / Q000378:metabolism*; D015640:Ion Channel Gating; D007473:Ion Channels / Q000378:metabolism*; D008051:Lipid Bilayers / Q000378:metabolism*; D009154:Mutation; D052899:Pore Forming Cytotoxic Proteins; D015032:Zinc / Q000494:pharmacology
D001427:Bacterial Toxins; D006460:Hemolysin Proteins; D007473:Ion Channels; D008051:Lipid Bilayers; D052899:Pore Forming Cytotoxic Proteins; C032676:aerolysin; D015032:Zinc