Clostridium perfringens beta-toxin forms potential-dependent, cation-selective channels in lipid bilayers.
Recombinant beta-toxin from Clostridium perfringens type C was found to increase the conductance of bilayer lipid membranes (BLMs) by inducing channel activity. The channels exhibited a distribution of conductances within the range of 10 to 380 pS, with the majority of the channels falling into two categories of conductance at 110 and 60 pS. The radii of beta-toxin pores found for the conductance states of 110 and 60 pS were 12.7 and 11.1 A, respectively. The single channels and the steady-state currents induced by beta-toxin across the BLMs exhibited ideal monovalent cation selectivity. Addition of divalent cations (Zn(2+), Cd(2+), or Mg(2+)) at a concentration of 2 mM increased the rate of beta-toxin insertion into BLMs and the single-channel conductance, while application of 5 mM Zn(2+) to a beta-toxin-induced steady-state current decreased the inward current by approximately 45%. The mutation of arginine 212 of beta-toxin to aspartate, previously shown to increase the 50% lethal dose of beta-toxin for mice nearly 13-fold, significantly reduced the ability of beta-toxin to form channels. These data support the hypothesis that the lethal action of beta-toxin is based on the formation of cation-selective pores in susceptible cells.
Shatursky
O
O
Department of Microbiology and Immunology, The University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73190, USA.
Bayles
R
R
Rogers
M
M
Jost
B H
BH
Songer
J G
JG
Tweten
R K
RK
D000818:Animals; D001427:Bacterial Toxins / Q000235:genetics / Q000633:toxicity*; D002412:Cations / Q000378:metabolism; D003015:Clostridium Infections / Q000382:microbiology; D003016:Clostridium perfringens / Q000378:metabolism / Q000472:pathogenicity*; D005260:Female; D007473:Ion Channels / Q000378:metabolism*; D008051:Lipid Bilayers / Q000378:metabolism*; D008564:Membrane Potentials; D051379:Mice; D011993:Recombinant Fusion Proteins / Q000633:toxicity; D013552:Swine
D001427:Bacterial Toxins; C031884:CPB protein, Clostridium perfringens; D002412:Cations; D007473:Ion Channels; D008051:Lipid Bilayers; D011993:Recombinant Fusion Proteins