An anion-selective analogue of the channel-forming peptide alamethicin.
The peptide alamethicin self-assembles to form helix bundle ion channels in membranes. Previous macroscopic measurements have shown that these channels are mildly cation-selective. Models indicate that a source of cation selectivity is a zone of partial negative charge toward the C-terminal end of the peptide. We synthesized an alamethicin derivative with a lysine in this zone (replacing the glutamine at position 18 in the sequence). Microscopic (single-channel) measurements demonstrate that dimeric alamethicin-lysine18 (alm-K18) forms mildly anion-selective channels under conditions where channels formed by the parent peptide are cation-selective. Long-range electrostatic interactions can explain the inversion of ion selectivity and the conductance properties of alamethicin channels.
D000408:Alamethicin / Q000138:chemical synthesis / Q000737:chemistry*; D000595:Amino Acid Sequence; D000838:Anions / Q000378:metabolism; D000900:Anti-Bacterial Agents / Q000138:chemical synthesis / Q000737:chemistry; D005249:Fees and Charges; D007473:Ion Channels / Q000138:chemical synthesis / Q000378:metabolism*; D008969:Molecular Sequence Data; D010452:Peptide Biosynthesis; D011189:Potassium Chloride / Q000378:metabolism; D017386:Sequence Homology, Amino Acid