[Energy profile of a channel formed by alpha-latrotoxin in a bilayer phospholipid membrane].

Current-voltage characteristics are obtained for a channel formed by alpha-latrotoxin when inserting into a bilayer lipid membrane separating solutions of different ionic composition. They are used for determining parameters of a two-barrier model of this channel energy profile. It is shown that selectivity of these channels is based on the same principles that in the calcium channels of biological membranes and is mainly determined by the ion binding inside the channel. Affinity of the channel for the penetrating ions of alkali-earth metals decreases in the sequence: Mg2+ greater than Ca2+ greater than Sr2+ approximately equal to Ba2+ and the blocking ability of the cations of transition metals increases in the series: Mn2+ less than Zn2+ approximately less than Ni2+ approximately less than Co2+ less than Cd2+ much less than La3+. The channel gives the monovalent ions to pass through as well, its permeability being dependent on the concentration of divalent ions from the cis-, but not from the trans-side of the membrane.