Two types of ion channel formation of tolaasin,a Pseudomonas peptide toxin

Tolaasin is a peptide toxin produced by Pseudomonas tolaasii and causes brown blotch disease of the cultivated mushrooms. Two types of ion channels were identified by the incorporation of tolaasin into lipid bilayer. The slope conductance of type 1 channel measured in the buffer containing 100 mM KCl was 150 pS with a linear current vs. voltage relationship. The type 2 tolaasin channel had two subconductance states of 300 and 500 pS. Both channels were inhibited by Zn(2+). Ion channel formations of tolaasin were concentration-dependent and single channel currents were successfully obtained at 0.6 unit tolaasin, 15.9 nM. The type 1 channel was obtained more frequently than the type 2 channel and the ratio of their appearance was approximately 4:1, respectively.