Comparative analysis of latrotoxin channels of different conductance in planar lipid bilayers. Evidence for cluster organization.

It has been established that channels induced by Latrodectus tredicimguttatus alpha-toxin (LT) in lipid bilayers have a cluster organisation. So far as: (i) the LT-channels had practically identical sizes of its water pores (r = 9.4 +/- 0.6 A) independently on the lipid composition of planar bilayer lipid membrane (BLM) although their conductances might differ from each other more than 10 times (100 mM KCl (pH 7.5)). (ii) affinity of permeable ions to channels had a small variation with distinct group of BLM, although LT-channels conductances varied from 112 +/- 8 pS till 1110 +/- 40 pS for phosphatidylcholine-BLM and from 75 +/- 6 pS till 170 +/- 14 pS for phosphatidylserine-BLM. (iii) Ca/K selectivity was greater in negatively charged membranes but did not also depend on the channel amplitude for the same BLM. Cation-anionic selectivity was identical for all studied channels.