Alamethicin (U-22324)

Alamethicin (U-22324) is a polypeptide natural product antibiotic supplied as a mixture of homologs: Alamethicin and Alamethicin I. These compounds form voltage-dependent ion channels in the lipid bilayer, through the spontaneous assembly of units into a multimeric barrel-stave structure spanning the membrane. This formation results in a hydrophilic pore which permits non-specific ion efflux through the membrane. The non-specific ion efflux obliterates the normal electrochemical gradient of the cell, producing the antibiotic property of Alamethicin. Substantiated by experiments with covalently tethered molecules of Alamethicin, It is suggested that different multimeric aggregation states create varying pore sizes with varying stabilities, correlating to differential specificity for ions. This channel-forming activity has been exploited as a tool for introducing hydrophilic small molecules into mitochondria without disrupting the integrity of the membrane.