Effective diameters of ion channels formed by homologs of the antibiotic chrysospermin

Radii of ion channels formed in the lipid bilayer by 4 homologs of the alamethicin-like Antibiotic, chrysospermin, were determined using hydrophilic nonelectrolytes. It is shown that the replacement of isovaline amino acid at position 15 of the polypeptide chain by alpha-aminoisobutyric acid results in the decrease in the channel effective radius from 1.2 +/- 0.15 to 0.94 +/- 0.1 nm and a respective 2.5-fold decrease in channel conductance.