Interaction of Clostridium botulinum C2 toxin with lipid bilayer membranes. Formation of cation-selective channels and inhibition of channel function by chloroquine.
Lipid bilayer experiments were performed with the C2-II binding component of the ADP-ribosylating C2 toxin from Clostridium botulinum. The trypsin-activated but not the nonactivated form of the protein was able to increase the specific conductance of artificial lipid bilayer membranes by the formation of ion-permeable channels. The channels had on average a single-channel conductance of 55 pS in 0.1 M KCl and were found to be cation-selective and voltage-dependent. The single-channel conductance was only moderately dependent on the bulk aqueous KCl concentration, which indicated point charge effects on the channel properties. Incubation of the activated C2-II binding component with antibodies against C2-II or with C2-I toxin inhibited channel formation to a large extent. Addition of chloroquine, a known inhibitor of endocytosis in cells, led to a dose-dependent decrease of the C2-II-induced membrane conductance. This result suggested that the activated C2-II component contains a binding site for chloroquine inside the channel. It is discussed that the channels formed by C2-II component are involved in the translocation of C2-I toxin across the target cell membrane.
Schmid
A
A
Lehrstuhl für Biotechnologie, Theodor-Boveri-Institut (Biozentrum), Universität Würzburg, Germany.
Benz
R
R
Just
I
I
Aktories
K
K
D000473:Alkanes; D001905:Botulinum Toxins / Q000378:metabolism*; D002738:Chloroquine / Q000494:pharmacology*; D004553:Electric Conductivity; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology*; D008051:Lipid Bilayers; D008433:Mathematics; D008954:Models, Biological; D010713:Phosphatidylcholines; D011336:Probability; D012492:Salts
D000473:Alkanes; D007473:Ion Channels; D008051:Lipid Bilayers; D010713:Phosphatidylcholines; D012492:Salts; C021016:1,2-diphytanoylphosphatidylcholine; D002738:Chloroquine; D001905:Botulinum Toxins; C012867:decane