EFFECTIVE DIAMETERS OF ION CHANNELS FORME D BY HOMOLOGS OF THE ANTIBIOTIC CHRYSOSPERMIN

Radii of ion channels formed in the lipid bilayer by four homologs of the alamethicin-like antibiotic chrysospermin, were determined using h ydrophylic nonelectrolytes. It is shown that replacement of isovaline amino acid at position 15 of the polypeptide chain by alpha-aminoisobu tyric acid results in the decrease in the channel effective radius fro m 1.2 +/- 0.15 to 0.94 +/- 0.1 nm and corresponding 2.5-fold decrease in the channel conductance.